diff --git a/webshell/embed/xlib/gtk/Makefile.in b/webshell/embed/xlib/gtk/Makefile.in
index 0a2523c2c6d2..934c08d4ad89 100644
--- a/webshell/embed/xlib/gtk/Makefile.in
+++ b/webshell/embed/xlib/gtk/Makefile.in
@@ -55,3 +55,5 @@ LIBS		= \
 			$(NULL)
 
 include $(topsrcdir)/config/rules.mk
+
+CXXFLAGS	+=	$(MOZ_GTK_CFLAGS)