diff --git a/libr/include/r_util/r_str.h b/libr/include/r_util/r_str.h
index 0e336a1971238..7bda3a9a7bdf2 100644
--- a/libr/include/r_util/r_str.h
+++ b/libr/include/r_util/r_str.h
@@ -38,8 +38,8 @@ R_API bool r_str_range_in(const char *r, ut64 addr);
 R_API int r_str_len_utf8(const char *s);
 R_API int r_str_len_utf8char(const char *s, int left);
 R_API void r_str_filter_zeroline(char *str, int len);
-R_API int r_str_utf8_codepoint (char* s, int left);
-R_API bool r_str_char_fullwidth (char* s, int left);
+R_API int r_str_utf8_codepoint (const char* s, int left);
+R_API bool r_str_char_fullwidth (const char* s, int left);
 R_API int r_str_write(int fd, const char *b);
 R_API void r_str_ncpy(char *dst, const char *src, int n);
 R_API void r_str_sanitize(char *c);
diff --git a/libr/util/str.c b/libr/util/str.c
index bafb177e504ae..4ec7ecd211302 100644
--- a/libr/util/str.c
+++ b/libr/util/str.c
@@ -1600,7 +1600,7 @@ R_API char *r_str_ansi_crop(const char *str, ut32 x, ut32 y, ut32 x2, ut32 y2) {
 	return ret;
 }
 
-R_API int r_str_utf8_codepoint (char* s, int left) {
+R_API int r_str_utf8_codepoint (const char* s, int left) {
 	bool safe = left >= 0;
 	if ((*s & 0x80) != 0x80) {
 		return 0;
@@ -1614,7 +1614,7 @@ R_API int r_str_utf8_codepoint (char* s, int left) {
 	return 0;
 }
 
-R_API bool r_str_char_fullwidth (char* s, int left) {
+R_API bool r_str_char_fullwidth (const char* s, int left) {
 	int codepoint = r_str_utf8_codepoint (s, left);
 	return (codepoint >= 0x1100 &&
 		 (codepoint <= 0x115f ||                  /* Hangul Jamo init. consonants */