diff --git a/packages/mongodb-constants/src/stage-operators.ts b/packages/mongodb-constants/src/stage-operators.ts
index 3c25c335..19f4d292 100644
--- a/packages/mongodb-constants/src/stage-operators.ts
+++ b/packages/mongodb-constants/src/stage-operators.ts
@@ -1260,6 +1260,7 @@ const STAGE_OPERATORS = [
     namespaces: [...ANY_NAMESPACE],
     description: 'Perform a union with a pipeline on another collection.',
     comment: `/**
+ * db: Optional. The target database name (MongoDB 9.0+).
  * coll: The collection name.
  * pipeline: The pipeline on the other collection.
  */