diff --git a/src/q931_decode.c b/src/q931_decode.c
index 9dd3c62..ea55f02 100644
--- a/src/q931_decode.c
+++ b/src/q931_decode.c
@@ -69,12 +69,12 @@ int q931_msg_parse(struct q931_msg_parsed *out, const uint8_t *buf, size_t len)
 
 	/* parse [variable length] call reference */
 	cref_len = buf[1] & 0x0F;
-	if (len < 2 + cref_len)
+	if (len < 2U + cref_len)
 		return -EMSGSIZE;
 	out->call_ref = q931_decode_callref(buf+1, len-1);
 
 	/* parse message type */
-	if (len < 2 + cref_len + 1)
+	if (len < 2U + cref_len + 1U)
 		return -EMSGSIZE;
 	out->msg_type = buf[2+cref_len] & 0x7f;