diff --git a/auth.go b/auth.go
index 4d8a6ce4..482c499a 100644
--- a/auth.go
+++ b/auth.go
@@ -31,7 +31,7 @@ func (a authPairs) searchCredential(authValue string) (string, bool) {
 		return "", false
 	}
 	for _, pair := range a {
-		if subtle.ConstantTimeCompare([]byte(pair.value), []byte(authValue)) == 1 {
+		if subtle.ConstantTimeCompare(bytesconv.StringToBytes(pair.value), bytesconv.StringToBytes(authValue)) == 1 {
 			return pair.user, true
 		}
 	}