diff --git a/lib/libforms/Makefile b/lib/libforms/Makefile
index b6ce00683c88..3703960c41aa 100644
--- a/lib/libforms/Makefile
+++ b/lib/libforms/Makefile
@@ -5,6 +5,8 @@ SRCS = forms.c parser.y lex.l menu.c fields.c
 CFLAGS += -I. -I${.CURDIR} -Wall -g -DHASH_STATS
 LDFLAGS += -ll
 
+CLEANFILES+= lex.c parser.c y.tab.h
+
 beforeinstall:
 	@(cd ${.CURDIR}; cmp -s forms.h ${DESTDIR}/usr/include/forms.h || \
 	   install -c -o ${BINOWN} -g ${BINGRP} -m 444 forms.h \