diff --git a/layout/macbuild/layoutSharedPrefix.h b/layout/macbuild/layoutSharedPrefix.h
index fbab20c0325..1a8bbaa6cd2 100644
--- a/layout/macbuild/layoutSharedPrefix.h
+++ b/layout/macbuild/layoutSharedPrefix.h
@@ -17,5 +17,6 @@
  */
 
 #define _IMPL_NS_LAYOUT 1
+#define INCLUDE_XUL 1
 
 #include "MacSharedPrefix.h"
diff --git a/layout/macbuild/layoutSharedPrefix_debug.h b/layout/macbuild/layoutSharedPrefix_debug.h
index c203d63d42c..87b02634579 100644
--- a/layout/macbuild/layoutSharedPrefix_debug.h
+++ b/layout/macbuild/layoutSharedPrefix_debug.h
@@ -17,5 +17,6 @@
  */
 
 #define _IMPL_NS_LAYOUT 1
+#define INCLUDE_XUL 1
 
 #include "MacSharedPrefix_debug.h"