--- ufo/include/ufo/gl/ugl_builtinfontrenderer.hpp
+++ ufo/include/ufo/gl/ugl_builtinfontrenderer.hpp
@@ -42,6 +42,7 @@
 
 class UFontPlugin;
 class UPluginBase;
+class UGL_BuiltinFontMetrics;
 
 // damn ms vc6
 struct UBuiltinFontStruct {