diff --git a/configure.in b/configure.in
index 75b39173382..02df4f1e525 100644
--- a/configure.in
+++ b/configure.in
@@ -1264,6 +1264,7 @@ xpfe/Makefile
 xpfe/AppCores/Makefile
 xpfe/AppCores/public/Makefile
 xpfe/AppCores/src/Makefile
+xpfe/AppCores/xul/Makefile
 xpfe/browser/Makefile
 xpfe/browser/public/Makefile
 xpfe/browser/src/Makefile