diff --git a/specification/_types/analysis/tokenizers.ts b/specification/_types/analysis/tokenizers.ts
index bdf63751cb..5eda956f0b 100644
--- a/specification/_types/analysis/tokenizers.ts
+++ b/specification/_types/analysis/tokenizers.ts
@@ -90,7 +90,7 @@ export class PathHierarchyTokenizer extends TokenizerBase {
   type: 'path_hierarchy'
   buffer_size: Stringified<integer>
   delimiter: string
-  replacement: string
+  replacement?: string
   reverse: Stringified<boolean>
   skip: Stringified<integer>
 }