diff --git a/glx/Makefile.am b/glx/Makefile.am
index f9a317853..8c705a74f 100644
--- a/glx/Makefile.am
+++ b/glx/Makefile.am
@@ -54,7 +54,7 @@ libglxdri_la_SOURCES = \
         extension_string.h
 
 if DRI2
-libglxdri_la_SOURCES = glxdri2.c
+libglxdri_la_SOURCES += glxdri2.c
 endif
 
 libglx_la_SOURCES = \