diff --git a/weed/s3api/auth_signature_v4.go b/weed/s3api/auth_signature_v4.go
index f15bac4a9..93bffdd34 100644
--- a/weed/s3api/auth_signature_v4.go
+++ b/weed/s3api/auth_signature_v4.go
@@ -602,7 +602,7 @@ func extractHostHeader(r *http.Request) string {
 		}
 
 		// An IPv6 address literal must be enclosed in square brackets.
-		if strings.Contains(forwardedHost, ":") && !strings.HasPrefix(forwardedHost, "[") {
+		if ip := net.ParseIP(forwardedHost); ip != nil && ip.To4() == nil {
 			forwardedHost = "[" + forwardedHost + "]"
 		}