diff --git a/libbb/getopt_ulflags.c b/libbb/getopt_ulflags.c
index 47f65d6b2..376893fc8 100644
--- a/libbb/getopt_ulflags.c
+++ b/libbb/getopt_ulflags.c
@@ -311,7 +311,7 @@ bb_getopt_ulflags (int argc, char **argv, const char *applet_opts, ...)
 	memset(on_off, 0, sizeof(complementally));
 
 	/* skip GNU extension */
-	s = applet_opts;
+	s = (const unsigned char *)applet_opts;
 	if(*s == '+' || *s == '-')
 		s++;
 	for (; *s; s++) {
@@ -345,7 +345,7 @@ bb_getopt_ulflags (int argc, char **argv, const char *applet_opts, ...)
 			c++;
 		}
 	}
-	for (s = bb_opt_complementally; s && *s; s++) {
+	for (s = (const unsigned char *)bb_opt_complementally; s && *s; s++) {
 		t_complementally *pair;
 		unsigned long *pair_switch;