diff --git a/src/Pay/LegacySignature.php b/src/Pay/LegacySignature.php
index 0a82824e5..4ae63b169 100644
--- a/src/Pay/LegacySignature.php
+++ b/src/Pay/LegacySignature.php
@@ -39,7 +39,8 @@ public function sign(array $params): array
                 ],
                 $params
             ),
-            static fn ($value, $key) => !($key === 'sign' || $value === '' || is_null($value))
+            static fn ($value, $key) => !($key === 'sign' || $value === '' || is_null($value)),
+            ARRAY_FILTER_USE_BOTH
         );
 
         ksort($attributes);