diff --git a/src/util/GLExt.cpp b/src/util/GLExt.cpp
index 6103248..81fae90 100644
--- a/src/util/GLExt.cpp
+++ b/src/util/GLExt.cpp
@@ -10,6 +10,7 @@
 #endif
 
 #if defined(__linux__) || defined(__FreeBSD__)
+#include <GL/glx.h>
 #include <dlfcn.h>
 #endif