diff --git a/src/Forms/GridField/GridFieldDetailForm_ItemRequest.php b/src/Forms/GridField/GridFieldDetailForm_ItemRequest.php
index a013b6b82..2486554b2 100644
--- a/src/Forms/GridField/GridFieldDetailForm_ItemRequest.php
+++ b/src/Forms/GridField/GridFieldDetailForm_ItemRequest.php
@@ -46,7 +46,7 @@ class GridFieldDetailForm_ItemRequest extends RequestHandler
      *
      * @var array
      */
-    private static $formActions;
+    private static $formActions = [];
 
     /**
      *