diff --git a/src/Limit.php b/src/Limit.php
index 0fc7134..5293353 100644
--- a/src/Limit.php
+++ b/src/Limit.php
@@ -67,7 +67,7 @@ public function key(): string
     {
         $prefix = 'fansipan_rate_limit';
 
-        return $prefix.''.$this->name;
+        return $prefix.'_'.$this->name;
     }
 
     public function maxAttempts(bool $includeThreshold = true): int