diff --git a/gfx/thebes/nsIOSurface.h b/gfx/thebes/nsIOSurface.h
index 69a8ac274f99..621e0b1eda4e 100644
--- a/gfx/thebes/nsIOSurface.h
+++ b/gfx/thebes/nsIOSurface.h
@@ -45,8 +45,6 @@
 
 class gfxASurface;
 class _CGLContextObject;
-// We would like to forward declare NSOpenGLContext, but it is an @interface and this
-// file is also used from c++.
 
 typedef _CGLContextObject* CGLContextObj;
 typedef uint32_t IOSurfaceID;
@@ -67,6 +65,8 @@ public:
   size_t GetBytesPerRow();
   void Lock();
   void Unlock();
+  // We would like to forward declare NSOpenGLContext, but it is an @interface
+  // and this file is also used from c++, so we use a void *.
   CGLError CGLTexImageIOSurface2D(void *ctxt,
                                   GLenum internalFormat, GLenum format,
                                   GLenum type, GLuint plane);