diff --git a/lib/libc/gen/strtofflags.c b/lib/libc/gen/strtofflags.c
index 596ef7b3601e..1edaa5a91154 100644
--- a/lib/libc/gen/strtofflags.c
+++ b/lib/libc/gen/strtofflags.c
@@ -82,7 +82,8 @@ fflagstostr(flags)
 	u_long flags;
 {
 	char *string;
-	char *sp, *dp;
+	const char *sp;
+	char *dp;
 	u_long setflags;
 	int i;