diff --git a/src/util/unicode.c b/src/util/unicode.c
index e4e7b0d61..cbc2db7cc 100644
--- a/src/util/unicode.c
+++ b/src/util/unicode.c
@@ -40,7 +40,7 @@ size_t unicode_utf8_trim(char *buf)
     assert(buf);
     while (*ip) {
         size_t size = 1;
-        wint_t wc = *ip;
+        wint_t wc = *(unsigned char *)ip;
         if (wc & 0x80) {
             wint_t ucs = 0;
             if (ip[1]) {