diff --git a/GL/glx/Makefile.am b/GL/glx/Makefile.am
index 2a76e04db..4ad2826f2 100644
--- a/GL/glx/Makefile.am
+++ b/GL/glx/Makefile.am
@@ -1,6 +1,6 @@
 noinst_LTLIBRARIES = libglx.la
 
-AM_CFLAGS = $(DIX_CFLAGS)
+AM_CFLAGS = $(DIX_CFLAGS) -I@MESA_SOURCE@/include
 
 # none yet
 #sdk_HEADERS =