diff --git a/src/Services/BookkeeperService.php b/src/Services/BookkeeperService.php
index a8bad576e..cabf58e24 100644
--- a/src/Services/BookkeeperService.php
+++ b/src/Services/BookkeeperService.php
@@ -64,6 +64,6 @@ public function increase(Wallet $wallet, $value): string
 
     private function getKey(Wallet $wallet): string
     {
-        return (string) $wallet->getKey();
+        return __CLASS__.'::'.$wallet->getKey();
     }
 }