diff --git a/specification/ingest/_types/Pipeline.ts b/specification/ingest/_types/Pipeline.ts
index da8a19de91..8863f1794c 100644
--- a/specification/ingest/_types/Pipeline.ts
+++ b/specification/ingest/_types/Pipeline.ts
@@ -41,7 +41,7 @@ export class Pipeline {
   /**
    * Arbitrary metadata about the ingest pipeline. This map is not automatically generated by Elasticsearch.
    */
-  _meta: Metadata
+  _meta?: Metadata
 }
 
 // Unused .. but let's keep it for now