diff --git a/src/Domain/Product/Repository/ExchangeRepoInterface.php b/src/Domain/Product/Repository/ExchangeRepoInterface.php
index 6cc3c4a..fb298df 100644
--- a/src/Domain/Product/Repository/ExchangeRepoInterface.php
+++ b/src/Domain/Product/Repository/ExchangeRepoInterface.php
@@ -16,8 +16,8 @@ interface ExchangeRepoInterface
     /**
      * @param PointType $source
      * @param PointType $target
-     * @param string $uid
+     * @param string|null $uid
      * @return float
      */
-    public function getRate(PointType $source, PointType $target, string $uid): float;
+    public function getRate(PointType $source, PointType $target, ?string $uid = null): float;
 }
\ No newline at end of file