Creating a patch for Windows

I want to create a header patch to fix my appveyor build. I used WinMerge to create the following file:

--- C:/Qt/5.3/mingw482_32/include/QtGui/qopengl.h   Thu Jun 19 11:08:06 2014
+++ C:/Qt/5.3/mingw482_32/include/QtGui/qopengl2.h  Sat Nov 08 11:20:32 2014
@@ -49,6 +49,7 @@
// Windows always needs this to ensure that APIENTRY gets defined
 #if defined(Q_OS_WIN)
 # include <QtCore/qt_windows.h>
+# undef MemoryBarrier
 #endif

 // Note: Mac OSX is a "controlled platform" for OpenGL ABI so we

      

        
        
        
      

    

When I run the patch command, I get the following output:

C:\Users\Martin\dev\TravisTest>patch -u patch_qopengl c:\Qt\5.3\mingw482_32\include\QtGui\qopengl.h
patch: **** Only garbage was found in the patch input.

      

        
        
        
      

    

What's wrong?