diff --git a/x-pack/plugins/maps/public/classes/sources/es_term_source/es_term_source.ts b/x-pack/plugins/maps/public/classes/sources/es_term_source/es_term_source.ts
index 813b8168a908e..9b711febcc992 100644
--- a/x-pack/plugins/maps/public/classes/sources/es_term_source/es_term_source.ts
+++ b/x-pack/plugins/maps/public/classes/sources/es_term_source/es_term_source.ts
@@ -56,7 +56,7 @@ export class ESTermSource extends AbstractESAggSource {
     }
     return {
       ...normalizedDescriptor,
-      term: descriptor.term,
+      term: descriptor!.term,
       type: SOURCE_TYPES.ES_TERM_SOURCE,
     };
   }