diff --git a/s3api/middlewares/authentication.go b/s3api/middlewares/authentication.go
index 41bf6496..bd9674be 100644
--- a/s3api/middlewares/authentication.go
+++ b/s3api/middlewares/authentication.go
@@ -51,8 +51,8 @@ func VerifyV4Signature(root RootUserConfig, iam auth.IAMService, region string,
 
 		// Check the signature version
 		authParts := strings.Split(authorization, ",")
-		for _, el := range authParts {
-			el = strings.TrimSpace(el)
+		for i, el := range authParts {
+			authParts[i] = strings.TrimSpace(el)
 		}
 
 		if len(authParts) != 3 {