diff --git a/netwerk/cache/nsCacheEntry.cpp b/netwerk/cache/nsCacheEntry.cpp
index f21556215819..1ac4c0c0410a 100644
--- a/netwerk/cache/nsCacheEntry.cpp
+++ b/netwerk/cache/nsCacheEntry.cpp
@@ -62,6 +62,7 @@ nsCacheEntry::nsCacheEntry(nsCString *          key,
       mLastModified(0),
       mExpirationTime(nsICache::NO_EXPIRATION_TIME),
       mFlags(0),
+      mPredictedDataSize(-1),
       mDataSize(0),
       mCacheDevice(nsnull),
       mData(nsnull)
diff --git a/netwerk/protocol/http/nsHttpChannel.cpp b/netwerk/protocol/http/nsHttpChannel.cpp
index c096e77a5369..8d599983224d 100644
--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -755,10 +755,20 @@ nsHttpChannel::CallOnStartRequest()
     if (mResponseHead && mResponseHead->ContentCharset().IsEmpty())
         mResponseHead->SetContentCharset(mContentCharsetHint);
 
-    if (mResponseHead)
+    if (mResponseHead) {
         SetPropertyAsInt64(NS_CHANNEL_PROP_CONTENT_LENGTH,
                            mResponseHead->ContentLength());
-
+        // If we have a cache entry, set its predicted size to ContentLength to
+        // avoid caching an entry that will exceed the max size limit.
+        if (mCacheEntry) {
+            nsresult rv;
+            PRInt64 predictedDataSize = -1; // -1 in case GetAsInt64 fails.
+            GetPropertyAsInt64(NS_CHANNEL_PROP_CONTENT_LENGTH, 
+                               &predictedDataSize);
+            rv = mCacheEntry->SetPredictedDataSize(predictedDataSize);
+            if (NS_FAILED(rv)) return rv;
+        }
+    }
     // Allow consumers to override our content type
     if ((mLoadFlags & LOAD_CALL_CONTENT_SNIFFERS) &&
         gIOService->GetContentSniffers().Count() != 0) {
@@ -2798,13 +2808,6 @@ nsHttpChannel::InitCacheEntry()
     rv = AddCacheEntryHeaders(mCacheEntry);
     if (NS_FAILED(rv)) return rv;
 
-    // set predicted size of entry so we do not store anything that will exceed
-    // the max entry size limit
-    PRInt64 predictedDataSize;
-    GetContentLength(&predictedDataSize);
-    rv = mCacheEntry->SetPredictedDataSize(predictedDataSize);
-    if (NS_FAILED(rv)) return rv;
-
     mInitedCacheEntry = PR_TRUE;
     return NS_OK;
 }