diff --git a/src/Entity/ShippingGateway.php b/src/Entity/ShippingGateway.php
index b2815b2..bca4829 100644
--- a/src/Entity/ShippingGateway.php
+++ b/src/Entity/ShippingGateway.php
@@ -114,14 +114,14 @@ public function getConfig(): ?array
     /**
      * {@inheritdoc}
      */
-    public function getConfigValue(string $key): ?string
+    public function getConfigValue(string $key)
     {
         Assert::keyExists($this->config, $key, sprintf(
             'Shipping gateway config named %s does not exist.',
             $key
         ));
 
-        return (string) $this->config[$key];
+        return $this->config[$key];
     }
 
     /**
diff --git a/src/Entity/ShippingGatewayInterface.php b/src/Entity/ShippingGatewayInterface.php
index cd54d10..81b6e67 100644
--- a/src/Entity/ShippingGatewayInterface.php
+++ b/src/Entity/ShippingGatewayInterface.php
@@ -53,7 +53,7 @@ public function getConfig(): ?array;
      *
      * @return string|null
      */
-    public function getConfigValue(string $key): ?string;
+    public function getConfigValue(string $key);
 
     /**
      * @return Collection|null