diff --git a/support/xhpast/Makefile b/support/xhpast/Makefile
--- a/support/xhpast/Makefile
+++ b/support/xhpast/Makefile
@@ -1,4 +1,4 @@
-BISONFLAGS = --verbose -d
+BISONFLAGS = --verbose -d -Wall
 CPPFLAGS   = -fPIC -Wall
 FLEXFLAGS  = -C