--- gfx/layers/composite/CompositableHost.cpp.orig	2020-09-12 21:47:42 UTC
+++ gfx/layers/composite/CompositableHost.cpp
@@ -13,6 +13,7 @@
 #include "ImageHost.h"  // for ImageHostBuffered, etc
 #include "Layers.h"
 #include "TiledContentHost.h"  // for TiledContentHost
+#include "mozilla/EndianUtils.h"
 #include "mozilla/gfx/gfxVars.h"
 #include "mozilla/layers/LayersSurfaces.h"  // for SurfaceDescriptor
 #include "mozilla/layers/TextureHost.h"     // for TextureHost, etc
@@ -92,9 +93,13 @@ bool CompositableHost::AddMaskEffect(EffectChain& aEff
   }
   MOZ_ASSERT(source);
 
+  // Setting an alpha-mask here breaks the URL-bar on big endian (s390x)
+  // if the typed URL is too long for the textbox (automatic scrolling needed)
+#if MOZ_LITTLE_ENDIAN()
   RefPtr<EffectMask> effect =
       new EffectMask(source, source->GetSize(), aTransform);
   aEffects.mSecondaryEffects[EffectTypes::MASK] = effect;
+#endif
   return true;
 }