diff --git a/lib/libc/rpc/Makefile.inc b/lib/libc/rpc/Makefile.inc
index 5c96968fa5a5..302a53fc40b5 100644
--- a/lib/libc/rpc/Makefile.inc
+++ b/lib/libc/rpc/Makefile.inc
@@ -17,7 +17,7 @@ SRCS+=	auth_des.c authdes_prot.c auth_time.c des_soft.c des_crypt.c \
 
 CFLAGS+= -DBROKEN_DES
 
-CLEANFILES= crypt_clnt.c crypt_xdr.c crypt.h
+CLEANFILES+= crypt_clnt.c crypt_xdr.c crypt.h
 
 RPCDIR= ${DESTDIR}/usr/include/rpcsvc
 RPCGEN= rpcgen -C