diff --git a/src/glut/glx/glutint.h b/src/glut/glx/glutint.h
index 7849a01acd5..71dceeceeee 100644
--- a/src/glut/glx/glutint.h
+++ b/src/glut/glx/glutint.h
@@ -30,7 +30,9 @@
 
 #ifndef _WIN32
 /* added by BrianP: */
+#ifndef APIENTRY
 #define APIENTRY GLAPIENTRY
+#endif
 #define __cdecl GLAPIENTRY
 #define CDECL GLAPIENTRY
 #endif