diff --git a/js/src/xpconnect/Makefile.in b/js/src/xpconnect/Makefile.in
index 7cb6ca39d554..808881decf71 100644
--- a/js/src/xpconnect/Makefile.in
+++ b/js/src/xpconnect/Makefile.in
@@ -20,7 +20,7 @@ srcdir		= @srcdir@
 
 include $(DEPTH)/config/autoconf.mk
 
-DIRS		= public src
+DIRS		= public idl src
 
 ifdef ENABLE_TESTS
 DIRS		+= tests shell