diff --git a/CMakeExternals/PatchVTK.cmake b/CMakeExternals/PatchVTK.cmake
index 46d60c3f7e..4eb6989741 100644
--- a/CMakeExternals/PatchVTK.cmake
+++ b/CMakeExternals/PatchVTK.cmake
@@ -1,3 +1,5 @@
 set(path "Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx")
 file(STRINGS ${path} contents NEWLINE_CONSUME)
 string(REPLACE "//#define GLX_GLXEXT_LEGACY" "#define GLX_GLXEXT_LEGACY" contents ${contents})
+set(CONTENTS ${contents})
+configure_file(${TEMPLATE_FILE} ${path} @ONLY)