diff --git a/wrap/gl/glu_tesselator.h b/wrap/gl/glu_tesselator.h
index 176cd555..62d34980 100644
--- a/wrap/gl/glu_tesselator.h
+++ b/wrap/gl/glu_tesselator.h
@@ -47,7 +47,7 @@ First Commit.
 //#include <GL/glu.h>
 
 #ifndef CALLBACK
-#ifdef WIN32
+#ifdef _WIN32
 #define CALLBACK __stdcall
 #else
 #define CALLBACK