--- a/gfx/layers/ipc/ShadowLayerUtilsX11.h
+++ b/gfx/layers/ipc/ShadowLayerUtilsX11.h
@@ -44,20 +44,20 @@ struct SurfaceDescriptorX11 {
     // the same valid XID, then size/format are "actually" the same
     // anyway, regardless of the values of the fields in
     // SurfaceDescriptorX11.
     return mId == aOther.mId;
   }
 
   already_AddRefed<gfxXlibSurface> OpenForeign() const;
 
-  Drawable mId;
-  XID mFormat; // either a PictFormat or VisualID
+  MOZ_INIT_OUTSIDE_CTOR Drawable mId;
+  MOZ_INIT_OUTSIDE_CTOR XID mFormat; // either a PictFormat or VisualID
   gfx::IntSize mSize;
-  Drawable mGLXPixmap; // used to prevent multiple bindings to the same GLXPixmap in-process
+  MOZ_INIT_OUTSIDE_CTOR Drawable mGLXPixmap; // used to prevent multiple bindings to the same GLXPixmap in-process
 };
 
 } // namespace layers
 } // namespace mozilla
 
 namespace IPC {
 
 template <>