diff --git a/rdf/base/Makefile.in b/rdf/base/Makefile.in
index bd699eb76147..3c686fb280e6 100644
--- a/rdf/base/Makefile.in
+++ b/rdf/base/Makefile.in
@@ -24,10 +24,9 @@ include $(DEPTH)/config/autoconf.mk
 
 DIRS = public src
 
-# Bug 4773. Removed for M4
-#ifdef BUILD_XPIDL
-#DIRS += idl
-#endif
+ifdef BUILD_XPIDL
+DIRS += idl
+endif
 
 include $(topsrcdir)/config/config.mk