--- a/gfx/layers/RotatedBuffer.cpp
+++ b/gfx/layers/RotatedBuffer.cpp
@@ -723,16 +723,22 @@ RotatedContentBuffer::BorrowDrawTargetFo
   }
   if (result->GetBackendType() == BackendType::DIRECT2D ||
       result->GetBackendType() == BackendType::DIRECT2D1_1) {
     drawPtr->SimplifyOutwardByArea(100 * 100);
   }
 
   if (aPaintState.mMode == SurfaceMode::SURFACE_COMPONENT_ALPHA) {
     MOZ_ASSERT(mDTBuffer && mDTBufferOnWhite);
+    if (!mDTBuffer || !mDTBufferOnWhite) {
+      // This can happen in release builds if allocating one of the two buffers
+      // failed. This is pretty bad and the reason for the failure is already
+      // reported through gfxCriticalError.
+      return nullptr;
+    }
     nsIntRegionRectIterator iter(*drawPtr);
     const nsIntRect *iterRect;
     while ((iterRect = iter.Next())) {
       mDTBuffer->FillRect(Rect(iterRect->x, iterRect->y, iterRect->width, iterRect->height),
                           ColorPattern(Color(0.0, 0.0, 0.0, 1.0)));
       mDTBufferOnWhite->FillRect(Rect(iterRect->x, iterRect->y, iterRect->width, iterRect->height),
                                  ColorPattern(Color(1.0, 1.0, 1.0, 1.0)));
     }