diff --git a/src/Builder/RelayBuilder.php b/src/Builder/RelayBuilder.php
index 7a69a20..b1bc99a 100644
--- a/src/Builder/RelayBuilder.php
+++ b/src/Builder/RelayBuilder.php
@@ -75,7 +75,7 @@ public function addBefore(string $key, array $middleware, string $beforeKey = nu
      */
     public function merge(string $key, array $middleware)
     {
-        if (array_key_exists($key, $this->middleware)) {
+        if (false === array_key_exists($key, $this->middleware)) {
             $this->middleware[$key] = $middleware;
             return $this;
         }