diff --git a/src/osg/glu/libtess/tess.h b/src/osg/glu/libtess/tess.h
index 17e9f3701..912cc5b9d 100644
--- a/src/osg/glu/libtess/tess.h
+++ b/src/osg/glu/libtess/tess.h
@@ -38,11 +38,15 @@
 // #include <GL/glu.h>
 #include <osg/GLU>
 
+// simply define GLAPIENTRY as nothing so that we can keep function signatures the same as declaration.
+#define GLAPIENTRY
+
 #include <setjmp.h>
 #include "mesh.h"
 #include "dict.h"
 #include "priorityq.h"
 
+
 /* The begin/end calls must be properly nested.  We keep track of
  * the current state to enforce the ordering.
  */
diff --git a/src/osg/glu/libutil/mipmap.cpp b/src/osg/glu/libutil/mipmap.cpp
index 1228c726d..7bc2ef6ba 100644
--- a/src/osg/glu/libutil/mipmap.cpp
+++ b/src/osg/glu/libutil/mipmap.cpp
@@ -30,6 +30,10 @@
 
 #include <osg/GLU>
 #include <osg/Image>
+#include <osg/Texture3D>
+
+// simply define GLAPIENTRY as nothing so that we can keep function signatures the same as declaration.
+#define GLAPIENTRY
 
 // #include "gluos.h"
 // #include <GL/glu.h>