diff --git a/netwerk/base/Dashboard.cpp b/netwerk/base/Dashboard.cpp
index fc9d7987477f..4868b52e701d 100644
--- a/netwerk/base/Dashboard.cpp
+++ b/netwerk/base/Dashboard.cpp
@@ -147,7 +147,10 @@ public:
     void StartTimer(uint32_t aTimeout);
     void StopTimer();
 
-    explicit ConnectionData(Dashboard *target)
+    explicit ConnectionData(Dashboard* target)
+        : mPort(0)
+        , mProtocol(nullptr)
+        , mTimeout(0)
     {
         mEventTarget = nullptr;
         mDashboard = target;
@@ -287,7 +290,11 @@ public:
     NS_DECL_THREADSAFE_ISUPPORTS
     NS_DECL_NSIDNSLISTENER
 
-    LookupHelper() = default;
+    LookupHelper()
+        : mEventTarget{ nullptr }
+        , mStatus{ NS_ERROR_NOT_INITIALIZED }
+    {
+    }
 
     nsresult ConstructAnswer(LookupArgument *aArgument);
 public:
diff --git a/netwerk/base/MemoryDownloader.cpp b/netwerk/base/MemoryDownloader.cpp
index 2aadf795f0c5..5a6bef065317 100644
--- a/netwerk/base/MemoryDownloader.cpp
+++ b/netwerk/base/MemoryDownloader.cpp
@@ -17,6 +17,7 @@ NS_IMPL_ISUPPORTS(MemoryDownloader,
 
 MemoryDownloader::MemoryDownloader(IObserver* aObserver)
 : mObserver(aObserver)
+, mStatus(NS_ERROR_NOT_INITIALIZED)
 {
 }
 
diff --git a/netwerk/base/Predictor.cpp b/netwerk/base/Predictor.cpp
index 7cb35d821fbf..2ed15e5d54f9 100644
--- a/netwerk/base/Predictor.cpp
+++ b/netwerk/base/Predictor.cpp
@@ -262,6 +262,9 @@ NS_IMPL_ISUPPORTS(Predictor,
 
 Predictor::Predictor()
   :mInitialized(false)
+  ,mCleanedUp(false)
+  ,mStartupTime(0)
+  ,mLastStartupTime(0)
   ,mStartupCount(1)
 {
   MOZ_ASSERT(!sSelf, "multiple Predictor instances!");
diff --git a/netwerk/base/RequestContextService.cpp b/netwerk/base/RequestContextService.cpp
index bd10d6d3cd09..9cdb2f071d67 100644
--- a/netwerk/base/RequestContextService.cpp
+++ b/netwerk/base/RequestContextService.cpp
@@ -464,7 +464,8 @@ RequestContextService *RequestContextService::sSelf = nullptr;
 NS_IMPL_ISUPPORTS(RequestContextService, nsIRequestContextService, nsIObserver)
 
 RequestContextService::RequestContextService()
-  : mNextRCID(1)
+  : mRCIDNamespace(0)
+  , mNextRCID(1)
 {
   MOZ_ASSERT(!sSelf, "multiple rcs instances!");
   MOZ_ASSERT(NS_IsMainThread());
diff --git a/netwerk/base/TCPFastOpenLayer.cpp b/netwerk/base/TCPFastOpenLayer.cpp
index f9fbf191aae4..787f4e1e1677 100644
--- a/netwerk/base/TCPFastOpenLayer.cpp
+++ b/netwerk/base/TCPFastOpenLayer.cpp
@@ -58,7 +58,17 @@ public:
     : mState(WAITING_FOR_CONNECT)
     , mFirstPacketBufLen(0)
     , mCondition(0)
-  {}
+  {
+    this->mAddr.raw.family = 0;
+    this->mAddr.inet.family = 0;
+    this->mAddr.inet.port = 0;
+    this->mAddr.inet.ip = 0;
+    this->mAddr.ipv6.family = 0;
+    this->mAddr.ipv6.port = 0;
+    this->mAddr.ipv6.flowinfo = 0;
+    this->mAddr.ipv6.scope_id = 0;
+    this->mAddr.local.family = 0;
+  }
 
   enum {
     CONNECTED,
diff --git a/netwerk/base/nsAsyncStreamCopier.cpp b/netwerk/base/nsAsyncStreamCopier.cpp
index 1b9031f6aa2d..b5441b1d8d4d 100644
--- a/netwerk/base/nsAsyncStreamCopier.cpp
+++ b/netwerk/base/nsAsyncStreamCopier.cpp
@@ -74,6 +74,8 @@ nsAsyncStreamCopier::nsAsyncStreamCopier()
     , mChunkSize(nsIOService::gDefaultSegmentSize)
     , mStatus(NS_OK)
     , mIsPending(false)
+    , mCloseSource{ false }
+    , mCloseSink{ false }
     , mShouldSniffBuffering(false)
 {
     LOG(("Creating nsAsyncStreamCopier @%p\n", this));
diff --git a/netwerk/base/nsBaseChannel.cpp b/netwerk/base/nsBaseChannel.cpp
index ea57c3407363..1a50a8e589f7 100644
--- a/netwerk/base/nsBaseChannel.cpp
+++ b/netwerk/base/nsBaseChannel.cpp
@@ -59,6 +59,7 @@ nsBaseChannel::nsBaseChannel()
   , mAllowThreadRetargeting(true)
   , mWaitingOnAsyncRedirect(false)
   , mOpenRedirectChannel(false)
+  , mRedirectFlags{ 0 }
   , mStatus(NS_OK)
   , mContentDispositionHint(UINT32_MAX)
   , mContentLength(-1)
diff --git a/netwerk/base/nsBufferedStreams.cpp b/netwerk/base/nsBufferedStreams.cpp
index 863e8b9ae569..60a6bf26fb54 100644
--- a/netwerk/base/nsBufferedStreams.cpp
+++ b/netwerk/base/nsBufferedStreams.cpp
@@ -46,7 +46,8 @@ using mozilla::Some;
 // nsBufferedStream
 
 nsBufferedStream::nsBufferedStream()
-    : mBuffer(nullptr),
+    : mBufferSize(0),
+      mBuffer(nullptr),
       mBufferStartOffset(0),
       mCursor(0),
       mFillPoint(0),
diff --git a/netwerk/base/nsIURIMutatorUtils.cpp b/netwerk/base/nsIURIMutatorUtils.cpp
index 0e02232b6e65..5908b0c40cd9 100644
--- a/netwerk/base/nsIURIMutatorUtils.cpp
+++ b/netwerk/base/nsIURIMutatorUtils.cpp
@@ -18,6 +18,7 @@ NS_MutateURI::NS_MutateURI(nsIURI* aURI)
 }
 
 NS_MutateURI::NS_MutateURI(const char * aContractID)
+  : mStatus(NS_ERROR_NOT_INITIALIZED)
 {
   mMutator = do_CreateInstance(aContractID, &mStatus);
   MOZ_ASSERT(NS_SUCCEEDED(mStatus), "Called with wrong aContractID");
diff --git a/netwerk/base/nsInputStreamPump.cpp b/netwerk/base/nsInputStreamPump.cpp
index 218a85c3412a..2c2a7923ed72 100644
--- a/netwerk/base/nsInputStreamPump.cpp
+++ b/netwerk/base/nsInputStreamPump.cpp
@@ -38,9 +38,13 @@ static mozilla::LazyLogModule gStreamPumpLog("nsStreamPump");
 nsInputStreamPump::nsInputStreamPump()
     : mState(STATE_IDLE)
     , mStreamOffset(0)
+    , mStreamLength(0)
+    , mSegSize(0)
+    , mSegCount(0)
     , mStatus(NS_OK)
     , mSuspendCount(0)
     , mLoadFlags(LOAD_NORMAL)
+    , mIsPending(false)
     , mProcessingCallbacks(false)
     , mWaitingForInputStreamReady(false)
     , mCloseWhenDone(false)
diff --git a/netwerk/base/nsPACMan.cpp b/netwerk/base/nsPACMan.cpp
index effcf5ac96f3..d3ec6e92a13b 100644
--- a/netwerk/base/nsPACMan.cpp
+++ b/netwerk/base/nsPACMan.cpp
@@ -277,6 +277,7 @@ PendingPACQuery::PendingPACQuery(nsPACMan* pacMan,
                                  nsPACManCallback* callback,
                                  bool mainThreadResponse)
   : Runnable("net::PendingPACQuery")
+  , mPort(0)
   , mPACMan(pacMan)
   , mCallback(callback)
   , mOnMainThreadOnly(mainThreadResponse)
diff --git a/netwerk/base/nsServerSocket.cpp b/netwerk/base/nsServerSocket.cpp
index c1df2e690653..521804d16f9e 100644
--- a/netwerk/base/nsServerSocket.cpp
+++ b/netwerk/base/nsServerSocket.cpp
@@ -44,6 +44,15 @@ nsServerSocket::nsServerSocket()
   , mAttached(false)
   , mKeepWhenOffline(false)
 {
+  this->mAddr.raw.family = 0;
+  this->mAddr.inet.family = 0;
+  this->mAddr.inet.port = 0;
+  this->mAddr.inet.ip = 0;
+  this->mAddr.ipv6.family = 0;
+  this->mAddr.ipv6.port = 0;
+  this->mAddr.ipv6.flowinfo = 0;
+  this->mAddr.ipv6.scope_id = 0;
+  this->mAddr.local.family = 0;
   // we want to be able to access the STS directly, and it may not have been
   // constructed yet.  the STS constructor sets gSocketTransportService.
   if (!gSocketTransportService)
diff --git a/netwerk/base/nsSocketTransport2.cpp b/netwerk/base/nsSocketTransport2.cpp
index a05c9d520b15..51986164e3e9 100644
--- a/netwerk/base/nsSocketTransport2.cpp
+++ b/netwerk/base/nsSocketTransport2.cpp
@@ -794,6 +794,10 @@ nsSocketTransport::nsSocketTransport()
     , mFirstRetryError(NS_OK)
     , mDoNotRetryToConnect(false)
 {
+    this->mNetAddr.raw.family = 0;
+    this->mNetAddr.inet = {};
+    this->mSelfAddr.raw.family = 0;
+    this->mSelfAddr.inet = {};
     SOCKET_LOG(("creating nsSocketTransport @%p\n", this));
 
     mTimeouts[TIMEOUT_CONNECT]    = UINT16_MAX; // no timeout
diff --git a/netwerk/base/nsStandardURL.h b/netwerk/base/nsStandardURL.h
index a5cf522cbdfa..e3b85cbcf537 100644
--- a/netwerk/base/nsStandardURL.h
+++ b/netwerk/base/nsStandardURL.h
@@ -474,7 +474,9 @@ public:
             return NS_OK;
         }
 
-        explicit TemplatedMutator() = default;
+        explicit TemplatedMutator() : mMarkedFileURL(false)
+        {
+        }
     private:
         virtual ~TemplatedMutator() = default;
 
diff --git a/netwerk/base/nsUDPSocket.cpp b/netwerk/base/nsUDPSocket.cpp
index 8c2d8ecaf488..17799739a90b 100644
--- a/netwerk/base/nsUDPSocket.cpp
+++ b/netwerk/base/nsUDPSocket.cpp
@@ -264,6 +264,7 @@ nsUDPSocket::nsUDPSocket()
   , mByteReadCount(0)
   , mByteWriteCount(0)
 {
+  this->mAddr.inet = {};
   mAddr.raw.family = PR_AF_UNSPEC;
   // we want to be able to access the STS directly, and it may not have been
   // constructed yet.  the STS constructor sets gSocketTransportService.
diff --git a/netwerk/cache/nsCacheEntry.cpp b/netwerk/cache/nsCacheEntry.cpp
index ad4a426fc9d5..d583c6026db0 100644
--- a/netwerk/cache/nsCacheEntry.cpp
+++ b/netwerk/cache/nsCacheEntry.cpp
@@ -27,13 +27,16 @@ nsCacheEntry::nsCacheEntry(const nsACString &   key,
       mFetchCount(0),
       mLastFetched(0),
       mLastModified(0),
+      mLastValidated(0),
       mExpirationTime(nsICache::NO_EXPIRATION_TIME),
       mFlags(0),
       mPredictedDataSize(-1),
       mDataSize(0),
       mCacheDevice(nullptr),
       mCustomDevice(nullptr),
-      mData(nullptr)
+      mData(nullptr),
+      mRequestQ{},
+      mDescriptorQ{}
 {
     MOZ_COUNT_CTOR(nsCacheEntry);
     PR_INIT_CLIST(this);
diff --git a/netwerk/cache/nsCacheEntryDescriptor.h b/netwerk/cache/nsCacheEntryDescriptor.h
index 668f1d7e4359..4fb0f76486ab 100644
--- a/netwerk/cache/nsCacheEntryDescriptor.h
+++ b/netwerk/cache/nsCacheEntryDescriptor.h
@@ -123,6 +123,7 @@ private:
           : nsInputStreamWrapper(desc, off)
           , mReadBuffer(nullptr)
           , mReadBufferLen(0)
+          , mZstream{}
           , mStreamInitialized(false)
           , mStreamEnded(false)
          {
@@ -203,6 +204,7 @@ private:
           : nsOutputStreamWrapper(desc, off)
           , mWriteBuffer(nullptr)
           , mWriteBufferLen(0)
+          , mZstream{}
           , mStreamInitialized(false)
           , mStreamEnded(false)
           , mUncompressedCount(0)
diff --git a/netwerk/cache/nsCacheService.cpp b/netwerk/cache/nsCacheService.cpp
index 5fd6cb396ac9..b020f4a89512 100644
--- a/netwerk/cache/nsCacheService.cpp
+++ b/netwerk/cache/nsCacheService.cpp
@@ -1103,9 +1103,11 @@ nsCacheService::nsCacheService()
       mClearingEntries(false),
       mEnableMemoryDevice(true),
       mEnableDiskDevice(true),
+      mEnableOfflineDevice(false),
       mMemoryDevice(nullptr),
       mDiskDevice(nullptr),
       mOfflineDevice(nullptr),
+      mDoomedEntries{},
       mTotalEntries(0),
       mCacheHits(0),
       mCacheMisses(0),
diff --git a/netwerk/cache/nsDiskCacheStreams.h b/netwerk/cache/nsDiskCacheStreams.h
index 937ba4be2e32..4736e5a5b771 100644
--- a/netwerk/cache/nsDiskCacheStreams.h
+++ b/netwerk/cache/nsDiskCacheStreams.h
@@ -43,7 +43,17 @@ public:
 
     // GCC 2.95.2 requires this to be defined, although we never call it.
     // and OS/2 requires that it not be private
-    nsDiskCacheStreamIO() { NS_NOTREACHED("oops"); }
+    nsDiskCacheStreamIO()
+        : mBinding(nullptr),
+          mDevice(nullptr),
+          mFD(nullptr),
+          mStreamEnd(0),
+          mBufSize(0),
+          mBuffer(nullptr),
+          mOutputStreamIsOpen(false)
+    {
+        NS_NOTREACHED("oops");
+    }
 
 private:
     virtual ~nsDiskCacheStreamIO();
diff --git a/netwerk/cache2/CacheFileIOManager.cpp b/netwerk/cache2/CacheFileIOManager.cpp
index b7e4fbb6e673..237eda56e052 100644
--- a/netwerk/cache2/CacheFileIOManager.cpp
+++ b/netwerk/cache2/CacheFileIOManager.cpp
@@ -1065,6 +1065,11 @@ public:
     , mHasHasAltData(false)
     , mHasOnStartTime(false)
     , mHasOnStopTime(false)
+    , mFrecency(0)
+    , mExpirationTime(0)
+    , mHasAltData(false)
+    , mOnStartTime(0)
+    , mOnStopTime(0)
   {
     if (aFrecency) {
       mHasFrecency = true;
@@ -4279,9 +4284,11 @@ public:
                         nsTArray<CacheFileHandle*> const& specialHandles)
     : Runnable("net::SizeOfHandlesRunnable")
     , mMonitor("SizeOfHandlesRunnable.mMonitor")
+    , mMonitorNotified(false)
     , mMallocSizeOf(mallocSizeOf)
     , mHandles(handles)
     , mSpecialHandles(specialHandles)
+    , mSize(0)
   {
   }
 
diff --git a/netwerk/cache2/CacheIndex.h b/netwerk/cache2/CacheIndex.h
index ff789a750259..89db3e8ce4ad 100644
--- a/netwerk/cache2/CacheIndex.h
+++ b/netwerk/cache2/CacheIndex.h
@@ -1209,6 +1209,7 @@ private:
     explicit DiskConsumptionObserver(nsWeakPtr const& aWeakObserver)
       : Runnable("net::CacheIndex::DiskConsumptionObserver")
       , mObserver(aWeakObserver)
+      , mSize(0)
     {
     }
     virtual ~DiskConsumptionObserver() {
diff --git a/netwerk/cache2/CacheStorageService.cpp b/netwerk/cache2/CacheStorageService.cpp
index bcad3f84bad3..a9f94bcfa79c 100644
--- a/netwerk/cache2/CacheStorageService.cpp
+++ b/netwerk/cache2/CacheStorageService.cpp
@@ -368,6 +368,7 @@ public:
     : WalkCacheRunnable(aVisitor, aVisitEntries)
     , mLoadInfo(aLoadInfo)
     , mPass(COLLECT_STATS)
+    , mCount(0)
   {
   }
 
@@ -396,6 +397,11 @@ private:
     explicit OnCacheEntryInfoRunnable(WalkDiskCacheRunnable* aWalker)
       : Runnable("net::WalkDiskCacheRunnable::OnCacheEntryInfoRunnable")
       , mWalker(aWalker)
+      , mDataSize(0)
+      , mFetchCount(0)
+      , mLastModifiedTime(0)
+      , mExpirationTime(0)
+      , mPinned(false)
     {
     }
 
@@ -1633,7 +1639,10 @@ public:
   NS_DECL_NSIRUNNABLE
 
   explicit CacheEntryDoomByKeyCallback(nsICacheEntryDoomCallback* aCallback)
-    : mCallback(aCallback) { }
+    : mCallback(aCallback)
+    , mResult(NS_ERROR_NOT_INITIALIZED)
+  {
+  }
 
 private:
   virtual ~CacheEntryDoomByKeyCallback();
diff --git a/netwerk/dns/DNS.cpp b/netwerk/dns/DNS.cpp
index 7d524cb46263..d958d5bf2209 100644
--- a/netwerk/dns/DNS.cpp
+++ b/netwerk/dns/DNS.cpp
@@ -283,6 +283,8 @@ NetAddr::operator < (const NetAddr& other) const
 
 NetAddrElement::NetAddrElement(const PRNetAddr *prNetAddr)
 {
+  this->mAddress.raw.family = 0;
+  this->mAddress.inet = {};
   PRNetAddrToNetAddr(prNetAddr, &mAddress);
 }
 
diff --git a/netwerk/dns/TRR.h b/netwerk/dns/TRR.h
index 3df505bf3ed8..61753b9ae6e6 100644
--- a/netwerk/dns/TRR.h
+++ b/netwerk/dns/TRR.h
@@ -108,6 +108,7 @@ public:
   explicit TRR(AHostResolver *aResolver, bool aPB)
     : mozilla::Runnable("TRR")
     , mHostResolver(aResolver)
+    , mType(TRRTYPE_A)
     , mBodySize(0)
     , mFailed(false)
     , mPB(aPB)
diff --git a/netwerk/dns/nsDNSService2.cpp b/netwerk/dns/nsDNSService2.cpp
index a663811bcc35..9f78c4609594 100644
--- a/netwerk/dns/nsDNSService2.cpp
+++ b/netwerk/dns/nsDNSService2.cpp
@@ -493,10 +493,16 @@ nsDNSService::nsDNSService()
     : mLock("nsDNSServer.mLock")
     , mDisableIPv6(false)
     , mDisablePrefetch(false)
+    , mBlockDotOnion(false)
     , mNotifyResolution(false)
     , mOfflineLocalhost(false)
     , mForceResolveOn(false)
+    , mProxyType(0)
     , mTrrService(nullptr)
+    , mResCacheEntries(0)
+    , mResCacheExpiration(0)
+    , mResCacheGrace(0)
+    , mResolverPrefsUpdated(false)
 {
 }
 
diff --git a/netwerk/dns/nsHostResolver.cpp b/netwerk/dns/nsHostResolver.cpp
index c6c9801d20a7..d70e64b7ac36 100644
--- a/netwerk/dns/nsHostResolver.cpp
+++ b/netwerk/dns/nsHostResolver.cpp
@@ -183,6 +183,7 @@ nsHostRecord::nsHostRecord(const nsHostKey& key)
     , addr_info(nullptr)
     , addr(nullptr)
     , negative(false)
+    , mResolverMode(MODE_NATIVEONLY)
     , mResolving(0)
     , mTRRSuccess(0)
     , mNativeSuccess(0)
diff --git a/netwerk/dns/nsIDNService.cpp b/netwerk/dns/nsIDNService.cpp
index f9f71635792a..1195c7f594be 100644
--- a/netwerk/dns/nsIDNService.cpp
+++ b/netwerk/dns/nsIDNService.cpp
@@ -141,6 +141,7 @@ void nsIDNService::prefsChanged(nsIPrefBranch *prefBranch, const char16_t *pref)
 nsIDNService::nsIDNService()
   : mLock("DNService pref value lock")
   , mShowPunycode(false)
+  , mRestrictionProfile(static_cast<restrictionProfile>(0))
   , mIDNUseWhitelist(false)
 {
   MOZ_ASSERT(NS_IsMainThread());
diff --git a/netwerk/ipc/NeckoMessageUtils.h b/netwerk/ipc/NeckoMessageUtils.h
index 26892416ac0c..ad60c4624ae8 100644
--- a/netwerk/ipc/NeckoMessageUtils.h
+++ b/netwerk/ipc/NeckoMessageUtils.h
@@ -27,7 +27,12 @@ struct Permission
   uint32_t capability, expireType;
   int64_t expireTime;
 
-  Permission() { }
+  Permission()
+    : capability(0)
+    , expireType(0)
+    , expireTime(0)
+  {}
+  
   Permission(const nsCString& aOrigin,
              const nsCString& aType,
              const uint32_t aCapability,
diff --git a/netwerk/protocol/file/nsFileChannel.cpp b/netwerk/protocol/file/nsFileChannel.cpp
index d12e0e309ddf..c97224d73c1d 100644
--- a/netwerk/protocol/file/nsFileChannel.cpp
+++ b/netwerk/protocol/file/nsFileChannel.cpp
@@ -257,7 +257,8 @@ nsFileUploadContentStream::OnCopyComplete()
 //-----------------------------------------------------------------------------
 
 nsFileChannel::nsFileChannel(nsIURI *uri)
-  : mFileURI(uri)
+  : mUploadLength(0)
+  , mFileURI(uri)
 {
 }
 
diff --git a/netwerk/protocol/ftp/nsFtpConnectionThread.cpp b/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
index efbd98eb57a7..b1eb78a97d4e 100644
--- a/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
+++ b/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
@@ -75,6 +75,7 @@ nsFtpState::nsFtpState()
     , mState(FTP_INIT)
     , mNextState(FTP_S_USER)
     , mKeepRunning(true)
+    , mResponseCode(0)
     , mReceivedControlData(false)
     , mTryingCachedControl(false)
     , mRETRFailed(false)
@@ -94,6 +95,8 @@ nsFtpState::nsFtpState()
     , mControlStatus(NS_OK)
     , mDeferredCallbackPending(false)
 {
+    this->mServerAddress.raw.family = 0;
+    this->mServerAddress.inet = {};
     LOG_INFO(("FTP:(%p) nsFtpState created", this));
 
     // make sure handler stays around
diff --git a/netwerk/protocol/ftp/nsFtpControlConnection.cpp b/netwerk/protocol/ftp/nsFtpControlConnection.cpp
index 8cc3cf081f33..491ae6b881c6 100644
--- a/netwerk/protocol/ftp/nsFtpControlConnection.cpp
+++ b/netwerk/protocol/ftp/nsFtpControlConnection.cpp
@@ -66,8 +66,12 @@ nsFtpControlConnection::OnInputStreamReady(nsIAsyncInputStream *stream)
 
 nsFtpControlConnection::nsFtpControlConnection(const nsACString& host,
                                                uint32_t port)
-    : mServerType(0), mSessionId(gFtpHandler->GetSessionId())
-    , mUseUTF8(false), mHost(host), mPort(port)
+    : mServerType(0)
+    , mSuspendedWrite(0)
+    , mSessionId(gFtpHandler->GetSessionId())
+    , mUseUTF8(false)
+    , mHost(host)
+    , mPort(port)
 {
     LOG_INFO(("FTP:CC created @%p", this));
 }
diff --git a/netwerk/protocol/http/Http2Compression.h b/netwerk/protocol/http/Http2Compression.h
index e7f46f1f3b8a..7bff09d93b73 100644
--- a/netwerk/protocol/http/Http2Compression.h
+++ b/netwerk/protocol/http/Http2Compression.h
@@ -100,6 +100,11 @@ class Http2Decompressor final : public Http2BaseCompressor
 {
 public:
   Http2Decompressor()
+    : mOffset(0)
+    , mData(nullptr)
+    , mDataLen(0)
+    , mSeenNonColonHeader(false)
+    , mIsPush(false)
   {
     mPeakSizeID = Telemetry::HPACK_PEAK_SIZE_DECOMPRESSOR;
     mPeakCountID = Telemetry::HPACK_PEAK_COUNT_DECOMPRESSOR;
diff --git a/netwerk/protocol/http/Http2Session.cpp b/netwerk/protocol/http/Http2Session.cpp
index 859bd39d0a22..e3417e0ffcba 100644
--- a/netwerk/protocol/http/Http2Session.cpp
+++ b/netwerk/protocol/http/Http2Session.cpp
@@ -114,6 +114,7 @@ Http2Session::Http2Session(nsISocketTransport *aSocketTransport, enum SpdyVersio
   , mLastReadEpoch(PR_IntervalNow())
   , mPingSentEpoch(0)
   , mPreviousUsed(false)
+  , mAggregatedHeaderSize(0)
   , mWaitingForSettingsAck(false)
   , mGoAwayOnPush(false)
   , mUseH2Deps(false)
diff --git a/netwerk/protocol/http/HttpBaseChannel.cpp b/netwerk/protocol/http/HttpBaseChannel.cpp
index 93961ebe05cb..ad644ddd7696 100644
--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -199,6 +199,7 @@ HttpBaseChannel::HttpBaseChannel()
   , mReferrerPolicy(NS_GetDefaultReferrerPolicy())
   , mRedirectCount(0)
   , mInternalRedirectCount(0)
+  , mChannelCreationTime(0)
   , mForcePending(false)
   , mCorsIncludeCredentials(false)
   , mCorsMode(nsIHttpChannelInternal::CORS_MODE_NO_CORS)
@@ -219,10 +220,13 @@ HttpBaseChannel::HttpBaseChannel()
   , mAltDataForChild(false)
   , mForceMainDocumentChannel(false)
   , mIsTrackingResource(false)
+  , mChannelId(0)
   , mLastRedirectFlags(0)
   , mReqContentLength(0U)
   , mPendingInputStreamLengthOperation(false)
 {
+  this->mSelfAddr.inet = {};
+  this->mPeerAddr.inet = {};
   LOG(("Creating HttpBaseChannel @%p\n", this));
 
   // Subfields of unions cannot be targeted in an initializer list.
diff --git a/netwerk/protocol/http/NullHttpChannel.cpp b/netwerk/protocol/http/NullHttpChannel.cpp
index f6a3500573c7..ef222b921012 100644
--- a/netwerk/protocol/http/NullHttpChannel.cpp
+++ b/netwerk/protocol/http/NullHttpChannel.cpp
@@ -15,6 +15,8 @@ NS_IMPL_ISUPPORTS(NullHttpChannel, nsINullChannel,
                   nsIHttpChannel, nsITimedChannel)
 
 NullHttpChannel::NullHttpChannel()
+  : mAllRedirectsSameOrigin(false)
+  , mAllRedirectsPassTimingAllowCheck(false)
 {
   mChannelCreationTime = PR_Now();
   mChannelCreationTimestamp = TimeStamp::Now();
@@ -22,6 +24,8 @@ NullHttpChannel::NullHttpChannel()
 }
 
 NullHttpChannel::NullHttpChannel(nsIHttpChannel * chan)
+  : mAllRedirectsSameOrigin(false)
+  , mAllRedirectsPassTimingAllowCheck(false)
 {
   nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
   ssm->GetChannelURIPrincipal(chan, getter_AddRefs(mResourcePrincipal));
diff --git a/netwerk/protocol/http/TunnelUtils.cpp b/netwerk/protocol/http/TunnelUtils.cpp
index db4b30bb9169..15d9faa557fa 100644
--- a/netwerk/protocol/http/TunnelUtils.cpp
+++ b/netwerk/protocol/http/TunnelUtils.cpp
@@ -43,7 +43,9 @@ TLSFilterTransaction::TLSFilterTransaction(nsAHttpTransaction *aWrapped,
   , mEncryptedTextSize(0)
   , mSegmentReader(aReader)
   , mSegmentWriter(aWriter)
+  , mFilterReadCode(NS_ERROR_NOT_INITIALIZED)
   , mForce(false)
+  , mReadSegmentBlocked(false)
   , mNudgeCounter(0)
 {
   MOZ_ASSERT(OnSocketThread(), "not on socket thread");
diff --git a/netwerk/protocol/http/nsCORSListenerProxy.cpp b/netwerk/protocol/http/nsCORSListenerProxy.cpp
index 53340cea9154..01fa8a012754 100644
--- a/netwerk/protocol/http/nsCORSListenerProxy.cpp
+++ b/netwerk/protocol/http/nsCORSListenerProxy.cpp
@@ -419,6 +419,9 @@ nsCORSListenerProxy::nsCORSListenerProxy(nsIStreamListener* aOuter,
     mWithCredentials(aWithCredentials && !gDisableCORSPrivateData),
     mRequestApproved(false),
     mHasBeenCrossSite(false),
+#ifdef DEBUG
+    mInited(false),
+#endif
     mMutex("nsCORSListenerProxy")
 {
 }
diff --git a/netwerk/protocol/http/nsHttpAuthCache.h b/netwerk/protocol/http/nsHttpAuthCache.h
index 98a10e06e35b..269479130d11 100644
--- a/netwerk/protocol/http/nsHttpAuthCache.h
+++ b/netwerk/protocol/http/nsHttpAuthCache.h
@@ -43,6 +43,8 @@ public:
                        const char16_t *user,
                        const char16_t *password)
         : mUser(nullptr)
+        , mPass{ nullptr }
+        , mDomain{ nullptr }
     {
         DebugOnly<nsresult> rv = Set(domain, user, password);
         MOZ_ASSERT(NS_SUCCEEDED(rv));
@@ -106,6 +108,8 @@ private:
         : mRoot(nullptr)
         , mTail(nullptr)
         , mRealm(nullptr)
+        , mCreds{ nullptr }
+        , mChallenge{ nullptr }
     {
         DebugOnly<nsresult> rv = Set(path, realm, creds, challenge, ident, metadata);
         MOZ_ASSERT(NS_SUCCEEDED(rv));
diff --git a/netwerk/protocol/http/nsHttpAuthManager.cpp b/netwerk/protocol/http/nsHttpAuthManager.cpp
index 3457be6741a1..4386f9efba1b 100644
--- a/netwerk/protocol/http/nsHttpAuthManager.cpp
+++ b/netwerk/protocol/http/nsHttpAuthManager.cpp
@@ -16,6 +16,12 @@ namespace net {
 
 NS_IMPL_ISUPPORTS(nsHttpAuthManager, nsIHttpAuthManager)
 
+nsHttpAuthManager::nsHttpAuthManager()
+  : mAuthCache(nullptr)
+  , mPrivateAuthCache(nullptr)
+{
+}
+
 nsresult nsHttpAuthManager::Init()
 {
   // get reference to the auth cache.  we assume that we will live
diff --git a/netwerk/protocol/http/nsHttpAuthManager.h b/netwerk/protocol/http/nsHttpAuthManager.h
index 4df1b936316a..331c5899484d 100644
--- a/netwerk/protocol/http/nsHttpAuthManager.h
+++ b/netwerk/protocol/http/nsHttpAuthManager.h
@@ -19,7 +19,7 @@ public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSIHTTPAUTHMANAGER
 
-  nsHttpAuthManager() = default;
+  nsHttpAuthManager();
   MOZ_MUST_USE nsresult Init();
 
 protected:
diff --git a/netwerk/protocol/http/nsHttpChannel.cpp b/netwerk/protocol/http/nsHttpChannel.cpp
index 60c4adcc3d32..1cfe7a188f0f 100644
--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -304,6 +304,7 @@ nsHttpChannel::nsHttpChannel()
     , mRequestTime(0)
     , mOfflineCacheLastModifiedTime(0)
     , mSuspendTotalTime(0)
+    , mRedirectType(0)
     , mCacheOpenWithPriority(false)
     , mCacheQueueSizeWhenOpen(0)
     , mCachedContentIsValid(false)
@@ -333,6 +334,7 @@ nsHttpChannel::nsHttpChannel()
     , mUsedNetwork(0)
     , mAuthConnectionRestartable(0)
     , mPushedStream(nullptr)
+    , mLocalBlocklist(false)
     , mOnTailUnblock(nullptr)
     , mWarningReporter(nullptr)
     , mIsReadingFromCache(false)
diff --git a/netwerk/protocol/http/nsHttpConnection.cpp b/netwerk/protocol/http/nsHttpConnection.cpp
index 2be2707e1dcc..18bc3f2678a8 100644
--- a/netwerk/protocol/http/nsHttpConnection.cpp
+++ b/netwerk/protocol/http/nsHttpConnection.cpp
@@ -46,9 +46,14 @@ namespace net {
 //-----------------------------------------------------------------------------
 
 nsHttpConnection::nsHttpConnection()
-    : mTransaction(nullptr)
+    : mSocketInCondition(NS_ERROR_NOT_INITIALIZED)
+    , mSocketOutCondition(NS_ERROR_NOT_INITIALIZED)
+    , mTransaction(nullptr)
     , mHttpHandler(gHttpHandler)
     , mCallbacksLock("nsHttpConnection::mCallbacksLock")
+    , mLastReadTime(0)
+    , mLastWriteTime(0)
+    , mMaxHangTime(0)
     , mConsiderReusedAfterInterval(0)
     , mConsiderReusedAfterEpoch(0)
     , mCurrentBytesRead(0)
@@ -56,6 +61,7 @@ nsHttpConnection::nsHttpConnection()
     , mTotalBytesRead(0)
     , mTotalBytesWritten(0)
     , mContentBytesWritten(0)
+    , mRtt(0)
     , mUrgentStartPreferred(false)
     , mUrgentStartPreferredKnown(false)
     , mConnectedTransport(false)
@@ -70,6 +76,7 @@ nsHttpConnection::nsHttpConnection()
     , mExperienced(false)
     , mInSpdyTunnel(false)
     , mForcePlainText(false)
+    , mTrafficCount(0)
     , mTrafficStamp(false)
     , mHttp1xTransactionCount(0)
     , mRemainingConnectionUses(0xffffffff)
diff --git a/netwerk/protocol/http/nsHttpConnectionMgr.cpp b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
index 9fe654c69b13..a12c35f790f0 100644
--- a/netwerk/protocol/http/nsHttpConnectionMgr.cpp
+++ b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
@@ -464,7 +464,14 @@ nsHttpConnectionMgr::DoShiftReloadConnectionCleanup(nsHttpConnectionInfo *aCI)
 class SpeculativeConnectArgs : public ARefBase
 {
 public:
-    SpeculativeConnectArgs() { mOverridesOK = false; }
+    SpeculativeConnectArgs()
+        : mParallelSpeculativeConnectLimit(0)
+        , mIgnoreIdle(false)
+        , mIsFromPredictor(false)
+        , mAllow1918(false)
+    {
+        mOverridesOK = false;
+    }
     NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SpeculativeConnectArgs, override)
 
 public: // intentional!
diff --git a/netwerk/protocol/http/nsHttpHandler.cpp b/netwerk/protocol/http/nsHttpHandler.cpp
index 1ab6b57091f1..82baba69f1f2 100644
--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -226,6 +226,7 @@ nsHttpHandler::nsHttpHandler()
     , mTailDelayQuantum(600)
     , mTailDelayQuantumAfterDCL(100)
     , mTailDelayMax(6000)
+    , mTailTotalMax(0)
     , mRedirectionLimit(10)
     , mPhishyUserPassLength(1)
     , mQoSBits(0x00)
diff --git a/netwerk/protocol/http/nsHttpNTLMAuth.h b/netwerk/protocol/http/nsHttpNTLMAuth.h
index 6beb3b67a7d5..c24b57f4f889 100644
--- a/netwerk/protocol/http/nsHttpNTLMAuth.h
+++ b/netwerk/protocol/http/nsHttpNTLMAuth.h
@@ -15,7 +15,7 @@ public:
     NS_DECL_ISUPPORTS
     NS_DECL_NSIHTTPAUTHENTICATOR
 
-    nsHttpNTLMAuth() = default;
+    nsHttpNTLMAuth() : mUseNative(false) {}
 
 private:
     virtual ~nsHttpNTLMAuth() = default;
diff --git a/netwerk/protocol/http/nsHttpTransaction.cpp b/netwerk/protocol/http/nsHttpTransaction.cpp
index c9824d83ce26..7eae2a51d9d4 100644
--- a/netwerk/protocol/http/nsHttpTransaction.cpp
+++ b/netwerk/protocol/http/nsHttpTransaction.cpp
@@ -146,6 +146,8 @@ nsHttpTransaction::nsHttpTransaction()
     , mEarlyDataDisposition(EARLY_NONE)
     , mFastOpenStatus(TFO_NOT_TRIED)
 {
+    this->mSelfAddr.inet = {};
+    this->mPeerAddr.inet = {};
     LOG(("Creating nsHttpTransaction @%p\n", this));
 
 #ifdef MOZ_VALGRIND
diff --git a/netwerk/protocol/viewsource/nsViewSourceChannel.h b/netwerk/protocol/viewsource/nsViewSourceChannel.h
index a8a8b6c1eb5d..694f09660064 100644
--- a/netwerk/protocol/viewsource/nsViewSourceChannel.h
+++ b/netwerk/protocol/viewsource/nsViewSourceChannel.h
@@ -46,7 +46,8 @@ public:
     // nsViewSourceChannel methods:
     nsViewSourceChannel()
         : mIsDocument(false)
-        , mOpened(false) {}
+        , mOpened(false)
+        , mIsSrcdocChannel(false) {}
 
     MOZ_MUST_USE nsresult Init(nsIURI* uri);
 
diff --git a/netwerk/protocol/websocket/WebSocketChannel.cpp b/netwerk/protocol/websocket/WebSocketChannel.cpp
index f94ea45cfdd4..4bf4982fb888 100644
--- a/netwerk/protocol/websocket/WebSocketChannel.cpp
+++ b/netwerk/protocol/websocket/WebSocketChannel.cpp
@@ -787,6 +787,28 @@ public:
     , mResetDeflater(false)
     , mMessageDeflated(false)
   {
+    this->mDeflater.next_in = nullptr;
+    this->mDeflater.avail_in = 0;
+    this->mDeflater.total_in = 0;
+    this->mDeflater.next_out = nullptr;
+    this->mDeflater.avail_out = 0;
+    this->mDeflater.total_out = 0;
+    this->mDeflater.msg = nullptr;
+    this->mDeflater.state = nullptr;
+    this->mDeflater.data_type = 0;
+    this->mDeflater.adler = 0;
+    this->mDeflater.reserved = 0;
+    this->mInflater.next_in = nullptr;
+    this->mInflater.avail_in = 0;
+    this->mInflater.total_in = 0;
+    this->mInflater.next_out = nullptr;
+    this->mInflater.avail_out = 0;
+    this->mInflater.total_out = 0;
+    this->mInflater.msg = nullptr;
+    this->mInflater.state = nullptr;
+    this->mInflater.data_type = 0;
+    this->mInflater.adler = 0;
+    this->mInflater.reserved = 0;
     MOZ_COUNT_CTOR(PMCECompression);
 
     mDeflater.zalloc = mInflater.zalloc = Z_NULL;
@@ -1158,6 +1180,7 @@ WebSocketChannel::WebSocketChannel() :
   mOpenTimeout(20000),
   mConnecting(NOT_CONNECTING),
   mMaxConcurrentConnections(200),
+  mInnerWindowID(0),
   mGotUpgradeOK(0),
   mRecvdHttpUpgradeTransport(0),
   mAutoFollowRedirects(0),
@@ -1184,6 +1207,8 @@ WebSocketChannel::WebSocketChannel() :
   mBufferSize(kIncomingBufferInitialSize),
   mCurrentOut(nullptr),
   mCurrentOutSent(0),
+  mHdrOutToSend(0),
+  mHdrOut(nullptr),
   mDynamicOutputSize(0),
   mDynamicOutput(nullptr),
   mPrivateBrowsing(false),
diff --git a/netwerk/socket/nsSOCKSIOLayer.cpp b/netwerk/socket/nsSOCKSIOLayer.cpp
index f18c0edc3cf6..6d5d6658489f 100644
--- a/netwerk/socket/nsSOCKSIOLayer.cpp
+++ b/netwerk/socket/nsSOCKSIOLayer.cpp
@@ -231,6 +231,7 @@ nsSOCKSSocketInfo::nsSOCKSSocketInfo()
     , mDataLength(0)
     , mReadOffset(0)
     , mAmountToRead(0)
+    , mLookupStatus(NS_ERROR_NOT_INITIALIZED)
     , mFD(nullptr)
     , mVersion(-1)
     , mDestinationFamily(AF_INET)
@@ -238,6 +239,24 @@ nsSOCKSSocketInfo::nsSOCKSSocketInfo()
     , mTlsFlags(0)
     , mTimeout(PR_INTERVAL_NO_TIMEOUT)
 {
+    this->mInternalProxyAddr.inet.family = 0;
+    this->mInternalProxyAddr.inet6.family = 0;
+    this->mInternalProxyAddr.inet6.port = 0;
+    this->mInternalProxyAddr.inet6.flowinfo = 0;
+    this->mInternalProxyAddr.inet6.scope_id = 0;
+    this->mInternalProxyAddr.local.family = 0;
+    this->mExternalProxyAddr.inet.family = 0;
+    this->mExternalProxyAddr.inet6.family = 0;
+    this->mExternalProxyAddr.inet6.port = 0;
+    this->mExternalProxyAddr.inet6.flowinfo = 0;
+    this->mExternalProxyAddr.inet6.scope_id = 0;
+    this->mExternalProxyAddr.local.family = 0;
+    this->mDestinationAddr.inet.family = 0;
+    this->mDestinationAddr.inet6.family = 0;
+    this->mDestinationAddr.inet6.port = 0;
+    this->mDestinationAddr.inet6.flowinfo = 0;
+    this->mDestinationAddr.inet6.scope_id = 0;
+    this->mDestinationAddr.local.family = 0;
     mData = new uint8_t[BUFFER_SIZE];
 
     mInternalProxyAddr.raw.family = AF_INET;
diff --git a/netwerk/streamconv/converters/nsDirIndexParser.cpp b/netwerk/streamconv/converters/nsDirIndexParser.cpp
index ee0b1e885242..8bc175ce1054 100644
--- a/netwerk/streamconv/converters/nsDirIndexParser.cpp
+++ b/netwerk/streamconv/converters/nsDirIndexParser.cpp
@@ -25,6 +25,11 @@ NS_IMPL_ISUPPORTS(nsDirIndexParser,
                   nsIStreamListener,
                   nsIDirIndexParser)
 
+nsDirIndexParser::nsDirIndexParser()
+  : mLineStart(0)
+  , mHasDescription(false) {
+}
+
 nsresult
 nsDirIndexParser::Init() {
   mLineStart = 0;
diff --git a/netwerk/streamconv/converters/nsDirIndexParser.h b/netwerk/streamconv/converters/nsDirIndexParser.h
index 18ce128d1bb2..694012a579a8 100644
--- a/netwerk/streamconv/converters/nsDirIndexParser.h
+++ b/netwerk/streamconv/converters/nsDirIndexParser.h
@@ -26,7 +26,7 @@ public:
     NS_DECL_NSIREQUESTOBSERVER
     NS_DECL_NSIDIRINDEXPARSER
 
-    nsDirIndexParser() = default;
+    nsDirIndexParser();
     nsresult Init();
 
     enum fieldType {
diff --git a/netwerk/streamconv/converters/nsHTTPCompressConv.cpp b/netwerk/streamconv/converters/nsHTTPCompressConv.cpp
index b06a4d16f506..cf71b5571aff 100644
--- a/netwerk/streamconv/converters/nsHTTPCompressConv.cpp
+++ b/netwerk/streamconv/converters/nsHTTPCompressConv.cpp
@@ -46,6 +46,8 @@ nsHTTPCompressConv::nsHTTPCompressConv()
   , mCheckHeaderDone(false)
   , mStreamEnded(false)
   , mStreamInitialized(false)
+  , mDummyStreamInitialised(false)
+  , d_stream{}
   , mLen(0)
   , hMode(0)
   , mSkipCount(0)
diff --git a/netwerk/streamconv/converters/nsHTTPCompressConv.h b/netwerk/streamconv/converters/nsHTTPCompressConv.h
index 50fe06e17a67..258865d0143c 100644
--- a/netwerk/streamconv/converters/nsHTTPCompressConv.h
+++ b/netwerk/streamconv/converters/nsHTTPCompressConv.h
@@ -61,6 +61,9 @@ public:
     : mTotalOut(0)
     , mStatus(NS_OK)
     , mBrotliStateIsStreamEnd(false)
+    , mRequest(nullptr)
+    , mContext(nullptr)
+    , mSourceOffset(0)
   {
     BrotliDecoderStateInit(&mState, 0, 0, 0);
   }
diff --git a/netwerk/streamconv/converters/nsIndexedToHTML.cpp b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
index f811a290ce28..7650283dde5d 100644
--- a/netwerk/streamconv/converters/nsIndexedToHTML.cpp
+++ b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
@@ -54,6 +54,11 @@ static void AppendNonAsciiToNCR(const nsAString& in, nsCString& out)
   }
 }
 
+nsIndexedToHTML::nsIndexedToHTML()
+    : mExpectAbsLoc(false)
+{
+}
+
 nsresult
 nsIndexedToHTML::Create(nsISupports *aOuter, REFNSIID aIID, void **aResult) {
     nsresult rv;
diff --git a/netwerk/streamconv/converters/nsIndexedToHTML.h b/netwerk/streamconv/converters/nsIndexedToHTML.h
index 30739c773b2e..8919747050a2 100644
--- a/netwerk/streamconv/converters/nsIndexedToHTML.h
+++ b/netwerk/streamconv/converters/nsIndexedToHTML.h
@@ -27,7 +27,7 @@ public:
     NS_DECL_NSISTREAMLISTENER
     NS_DECL_NSIDIRINDEXLISTENER
 
-    nsIndexedToHTML() = default;
+    nsIndexedToHTML();
 
     nsresult Init(nsIStreamListener *aListener);
 
diff --git a/netwerk/streamconv/converters/nsMultiMixedConv.cpp b/netwerk/streamconv/converters/nsMultiMixedConv.cpp
index 17f5b98de506..1dafb66d8b9b 100644
--- a/netwerk/streamconv/converters/nsMultiMixedConv.cpp
+++ b/netwerk/streamconv/converters/nsMultiMixedConv.cpp
@@ -27,6 +27,8 @@ nsPartChannel::nsPartChannel(nsIChannel *aMultipartChannel, uint32_t aPartID,
   mMultipartChannel(aMultipartChannel),
   mListener(aListener),
   mStatus(NS_OK),
+  mLoadFlags(0),
+  mContentDisposition(0),
   mContentLength(UINT64_MAX),
   mIsByteRangeRequest(false),
   mByteRangeStart(0),
@@ -813,6 +815,7 @@ nsMultiMixedConv::SwitchToControlParsing()
 nsMultiMixedConv::nsMultiMixedConv() :
     mCurrentPartID(0),
     mInOnDataAvailable(false),
+    mResponseHeader(HEADER_UNKNOWN),
     // XXX: This is a hack to bypass the raw pointer to refcounted object in
     // lambda analysis. It should be removed and replaced when the
     // IncrementalTokenizer API is improved to avoid the need for such
diff --git a/netwerk/test/TestUDPSocket.cpp b/netwerk/test/TestUDPSocket.cpp
index ce54a7064618..ca2ce48bc4ff 100644
--- a/netwerk/test/TestUDPSocket.cpp
+++ b/netwerk/test/TestUDPSocket.cpp
@@ -213,7 +213,8 @@ protected:
 
 public:
   explicit MulticastTimerCallback(WaitForCondition* waiter)
-    : mWaiter(waiter)
+    : mResult(NS_ERROR_NOT_INITIALIZED)
+    , mWaiter(waiter)
   { }
 
   NS_DECL_THREADSAFE_ISUPPORTS