--- a/gfx/layers/ipc/ShadowLayerUtilsX11.h
+++ b/gfx/layers/ipc/ShadowLayerUtilsX11.h
@@ -23,17 +23,20 @@ class gfxXlibSurface;
 namespace IPC {
 class Message;
 }
 
 namespace mozilla {
 namespace layers {
 
 struct SurfaceDescriptorX11 {
-  SurfaceDescriptorX11()
+  SurfaceDescriptorX11() 
+    : mId(0)
+    , mFormat(0)
+    , mGLXPixmap(0)
   { }
 
   explicit SurfaceDescriptorX11(gfxXlibSurface* aSurf, bool aForwardGLX = false);
 
   SurfaceDescriptorX11(Drawable aDrawable, XID aFormatID,
                        const gfx::IntSize& aSize);
 
   // Default copy ctor and operator= are OK