diff --git a/src/operations/create_collection.ts b/src/operations/create_collection.ts
index 86291c646a..5fcc33682c 100644
--- a/src/operations/create_collection.ts
+++ b/src/operations/create_collection.ts
@@ -37,7 +37,7 @@ const ILLEGAL_COMMAND_FIELDS = new Set([
 export interface TimeSeriesCollectionOptions extends Document {
   timeField: string;
   metaField?: string;
-  granularity?: string;
+  granularity?: 'seconds' | 'minutes' | 'hours' | string;
 }
 
 /** @public */