--- a/netwerk/protocol/http/Http2Session.cpp
+++ b/netwerk/protocol/http/Http2Session.cpp
@@ -1079,16 +1079,17 @@ Http2Session::RecvHeaders(Http2Session *
 
   // Find out how much padding this frame has, so we can only extract the real
   // header data from the frame.
   uint16_t paddingLength = 0;
   uint8_t paddingControlBytes = 0;
   nsresult rv;
 
   if (!isContinuation) {
+    self->mDecompressBuffer.Truncate();
     rv = self->ParsePadding(paddingControlBytes, paddingLength);
     if (NS_FAILED(rv)) {
       return rv;
     }
   }
 
   LOG3(("Http2Session::RecvHeaders %p stream 0x%X priorityLen=%d stream=%p "
         "end_stream=%d end_headers=%d priority_group=%d "
@@ -1386,16 +1387,17 @@ Http2Session::RecvPushPromise(Http2Sessi
   // frame to be PUSH_PROMISE of the same ID
   uint32_t promiseLen;
   uint32_t promisedID;
 
   if (self->mExpectedPushPromiseID) {
     promiseLen = 0; // really a continuation frame
     promisedID = self->mContinuedPromiseStream;
   } else {
+    self->mDecompressBuffer.Truncate();
     nsresult rv = self->ParsePadding(paddingControlBytes, paddingLength);
     if (NS_FAILED(rv)) {
       return rv;
     }
     promiseLen = 4;
     promisedID =
       PR_ntohl(*reinterpret_cast<uint32_t *>(self->mInputFrameBuffer.get() + 8 + paddingControlBytes));
     promisedID &= 0x7fffffff;