diff --git a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
index 290cdb749..ae063ead1 100644
--- a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
+++ b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
@@ -136,7 +136,7 @@ class GridFieldAddExistingAutocompleter implements GridField_HTMLProvider, GridF
 
         // If an object is not found, disable the action
         if (!is_int($gridField->State->GridFieldAddRelation(null))) {
-            $addAction->setReadonly(true);
+            $addAction->setDisabled(true);
         }
 
         $forTemplate->Fields->push($searchField);