# HG changeset patch
# User Timothy Nikkel <tnikkel@gmail.com>
# Parent  0e5e012ca28549fb00b1125fcaf3f6693ebf72e3
Bug 1242093.

diff --git a/image/decoders/nsBMPDecoder.cpp b/image/decoders/nsBMPDecoder.cpp
--- a/image/decoders/nsBMPDecoder.cpp
+++ b/image/decoders/nsBMPDecoder.cpp
@@ -969,17 +969,17 @@ nsBMPDecoder::ReadRLESegment(const char*
 LexerTransition<nsBMPDecoder::State>
 nsBMPDecoder::ReadRLEDelta(const char* aData)
 {
   // Delta encoding makes it possible to skip pixels making part of the image
   // transparent.
   MOZ_ASSERT(mMayHaveTransparency);
   mDoesHaveTransparency = true;
 
-  if (mDownscaler) {
+  if (mDownscaler && mCurrentPos < mH.mWidth) {
     // Clear the skipped pixels. (This clears to the end of the row,
     // which is perfect if there's a Y delta and harmless if not).
     mDownscaler->ClearRow(/* aStartingAtCol = */ mCurrentPos);
   }
 
   // Handle the XDelta.
   mCurrentPos += uint8_t(aData[0]);
   if (mCurrentPos > mH.mWidth) {