diff --git a/lib/dns/spnego.c b/lib/dns/spnego.c
index 77a8c31e91..59b3cbe4bf 100644
--- a/lib/dns/spnego.c
+++ b/lib/dns/spnego.c
@@ -1229,7 +1229,7 @@ der_put_oid(unsigned char *p, size_t len,
 	unsigned char *base = p;
 	size_t n;
 
-	for (n = data->length - 1; n >= 2; --n) {
+	for (n = data->length - 1; n >= 2u; --n) {
 		unsigned	u = data->components[n];
 
 		if (len < 1U)