diff --git a/util.c b/util.c
index ebfafa1..251c9d1 100644
--- a/util.c
+++ b/util.c
@@ -456,7 +456,7 @@ static const uint16_t util_crc16_table[8][256] = {{
 }};
 
 /* Non - Reflected */
-uint16_t util_crc16(uint16_t current, const char *k, size_t len) {
+uint16_t util_crc16(uint16_t current, const char *GMQCC_RESTRICT k, size_t len) {
     register uint16_t h = current;
 
     /* don't load twice */