diff --git a/js/src/vm/Stopwatch.cpp b/js/src/vm/Stopwatch.cpp
index c06724a8edb1..faa37f765f79 100644
--- a/js/src/vm/Stopwatch.cpp
+++ b/js/src/vm/Stopwatch.cpp
@@ -221,8 +221,10 @@ AutoStopwatch::AutoStopwatch(JSContext* cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IM
     }
     for (auto group = groups->begin(); group < groups->end(); group++) {
       auto acquired = acquireGroup(*group);
-      if (acquired)
-        groups_.append(acquired);
+      if (acquired) {
+          if (!groups_.append(acquired))
+              MOZ_CRASH();
+      }
     }
     if (groups_.length() == 0) {
       // We are not in charge of monitoring anything.
diff --git a/toolkit/components/perfmonitoring/nsPerformanceStats.cpp b/toolkit/components/perfmonitoring/nsPerformanceStats.cpp
index d2c759943a22..187164e8a040 100644
--- a/toolkit/components/perfmonitoring/nsPerformanceStats.cpp
+++ b/toolkit/components/perfmonitoring/nsPerformanceStats.cpp
@@ -164,7 +164,9 @@ nsPerformanceObservationTarget::SetTarget(nsPerformanceGroupDetails* details) {
 
 NS_IMETHODIMP
 nsPerformanceObservationTarget::AddJankObserver(nsIPerformanceObserver* observer) {
-  mObservers.append(observer);
+  if (!mObservers.append(observer)) {
+    MOZ_CRASH();
+  }
   return NS_OK;
 };
 
@@ -188,7 +190,9 @@ void
 nsPerformanceObservationTarget::NotifyJankObservers(nsIPerformanceGroupDetails* source, nsIPerformanceAlert* gravity) {
   // Copy the vector to make sure that it won't change under our feet.
   mozilla::Vector<nsCOMPtr<nsIPerformanceObserver>> observers;
-  observers.appendAll(mObservers);
+  if (!observers.appendAll(mObservers)) {
+    MOZ_CRASH();
+  }
 
   // Now actually notify.
   for (auto iter = observers.begin(), end = observers.end(); iter < end; ++iter) {
@@ -733,7 +737,9 @@ nsPerformanceStatsService::Dispose()
   // not modify the hashtable while iterating it.
   GroupVector groups;
   for (auto iter = mGroups.Iter(); !iter.Done(); iter.Next()) {
-    groups.append(iter.Get()->GetKey());
+    if (!groups.append(iter.Get()->GetKey())) {
+      MOZ_CRASH();
+    }
   }
   for (auto iter = groups.begin(), end = groups.end(); iter < end; ++iter) {
     RefPtr<nsPerformanceGroup> group = *iter;
@@ -1007,7 +1013,10 @@ nsPerformanceStatsService::GetPerformanceGroups(JSContext* cx, JSGroupVector& ou
   }
 
   // All compartments belong to the top group.
-  out.append(mTopGroup);
+  if (!out.append(mTopGroup)) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
 
   nsAutoString name;
   CompartmentName(cx, global, name);
@@ -1032,7 +1041,10 @@ nsPerformanceStatsService::GetPerformanceGroups(JSContext* cx, JSGroupVector& ou
                                           nsPerformanceGroup::GroupScope::ADDON)
                  );
     }
-    out.append(entry->GetGroup());
+    if (!out.append(entry->GetGroup())) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
   }
 
   // Find out if the compartment is executed by a window. If so, its
@@ -1054,7 +1066,10 @@ nsPerformanceStatsService::GetPerformanceGroups(JSContext* cx, JSGroupVector& ou
                                           nsPerformanceGroup::GroupScope::WINDOW)
                  );
     }
-    out.append(entry->GetGroup());
+    if (!out.append(entry->GetGroup())) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
   }
 
   // All compartments have their own group.
@@ -1063,7 +1078,10 @@ nsPerformanceStatsService::GetPerformanceGroups(JSContext* cx, JSGroupVector& ou
                              name, addonId, windowId,
                              mProcessId, isSystem,
                              nsPerformanceGroup::GroupScope::COMPARTMENT);
-  out.append(group);
+  if (!out.append(group)) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
 
   return true;
 }
@@ -1190,8 +1208,9 @@ nsPerformanceStatsService::CommitGroup(uint64_t iteration,
 
   if (totalTimeDelta >= mJankAlertThreshold) {
     if (!group->HasPendingAlert()) {
-      group->SetHasPendingAlert(true);
-      mPendingAlerts.append(group);
+      if (mPendingAlerts.append(group)) {
+        group->SetHasPendingAlert(true);
+      }
       return;
     }
   }
diff --git a/toolkit/components/telemetry/Telemetry.cpp b/toolkit/components/telemetry/Telemetry.cpp
index 3a57c38f0ff8..7387e280d302 100644
--- a/toolkit/components/telemetry/Telemetry.cpp
+++ b/toolkit/components/telemetry/Telemetry.cpp
@@ -16,6 +16,7 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/Likely.h"
 #include "mozilla/MathAlgorithms.h"
+#include "mozilla/unused.h"
 
 #include "base/histogram.h"
 #include "base/pickle.h"
@@ -3669,7 +3670,8 @@ TelemetryImpl::RecordThreadHangStats(Telemetry::ThreadHangStats& aStats)
 
   MutexAutoLock autoLock(sTelemetry->mThreadHangStatsMutex);
 
-  sTelemetry->mThreadHangStats.append(Move(aStats));
+  // Ignore OOM.
+  mozilla::Unused << sTelemetry->mThreadHangStats.append(Move(aStats));
 }
 
 NS_IMPL_ISUPPORTS(TelemetryImpl, nsITelemetry, nsIMemoryReporter)
diff --git a/toolkit/components/telemetry/ThreadHangStats.h b/toolkit/components/telemetry/ThreadHangStats.h
index 6ab077fa62ce..60aa680c87da 100644
--- a/toolkit/components/telemetry/ThreadHangStats.h
+++ b/toolkit/components/telemetry/ThreadHangStats.h
@@ -187,7 +187,9 @@ public:
   void Add(PRIntervalTime aTime, HangMonitor::HangAnnotationsPtr aAnnotations) {
     TimeHistogram::Add(aTime);
     if (aAnnotations) {
-      mAnnotations.append(Move(aAnnotations));
+      if (!mAnnotations.append(Move(aAnnotations))) {
+        MOZ_CRASH();
+      }
     }
   }
 };
diff --git a/xpcom/threads/BackgroundHangMonitor.cpp b/xpcom/threads/BackgroundHangMonitor.cpp
index 3b5ccc4c4bfd..06d39b7f282a 100644
--- a/xpcom/threads/BackgroundHangMonitor.cpp
+++ b/xpcom/threads/BackgroundHangMonitor.cpp
@@ -437,7 +437,9 @@ BackgroundHangThread::ReportHang(PRIntervalTime aHangTime)
   }
   // Add new histogram
   newHistogram.Add(aHangTime, Move(mAnnotations));
-  mStats.mHangs.append(Move(newHistogram));
+  if (!mStats.mHangs.append(Move(newHistogram))) {
+    MOZ_CRASH();
+  }
   return mStats.mHangs.back();
 }