diff --git a/RouteDescriber/FosRestDescriber.php b/RouteDescriber/FosRestDescriber.php
index 4a6e8f9..1a4615f 100644
--- a/RouteDescriber/FosRestDescriber.php
+++ b/RouteDescriber/FosRestDescriber.php
@@ -63,7 +63,7 @@ final class FosRestDescriber implements RouteDescriberInterface
     private function normalizeRequirements($requirements)
     {
         // if pattern
-        if (isset($requirements['rule'])) {
+        if (is_array($requirements) && isset($requirements['rule'])) {
             return (string) $requirements['rule'];
         }
         if (is_string($requirements)) {