diff --git a/CRM/Core/CodeGen/Specification.php b/CRM/Core/CodeGen/Specification.php
index b4f2c26f48a1..719db4ee5243 100644
--- a/CRM/Core/CodeGen/Specification.php
+++ b/CRM/Core/CodeGen/Specification.php
@@ -706,7 +706,7 @@ public function getDynamicForeignKey(&$foreignXML, &$dynamicForeignKeys) {
     $foreignKey = [
       'idColumn' => trim($foreignXML->idColumn),
       'typeColumn' => trim($foreignXML->typeColumn),
-      'key' => trim($this->value('key', $foreignXML)),
+      'key' => trim($this->value('key', $foreignXML) ?? ''),
     ];
     $dynamicForeignKeys[] = $foreignKey;
   }