diff --git a/src/Definition/RuntimeDefinition.php b/src/Definition/RuntimeDefinition.php
index e8d7dede..d5942d80 100644
--- a/src/Definition/RuntimeDefinition.php
+++ b/src/Definition/RuntimeDefinition.php
@@ -94,7 +94,7 @@ public function hasClass($class)
             return (array_key_exists($class, $this->classes));
         }
         
-        return class_exists($class, true);
+        return class_exists($class) || interface_exists($class);
     }
 
     /**