diff --git a/include/extinit.h b/include/extinit.h
index 64feaa7a8..69559f9d2 100644
--- a/include/extinit.h
+++ b/include/extinit.h
@@ -53,6 +53,7 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 #include "extnsionst.h"
 
+/* required by: libglx */
 #ifdef COMPOSITE
 extern _X_EXPORT Bool noCompositeExtension;
 #endif