diff --git a/lib/models/room-state.js b/lib/models/room-state.js
index b93f7933b..aabd1214d 100644
--- a/lib/models/room-state.js
+++ b/lib/models/room-state.js
@@ -187,6 +187,11 @@ RoomState.prototype.getLastModifiedTime = function() {
     return this._modified;
 };
 
+/**
+ * Get user IDs with the specified display name.
+ * @param {string} displayName The display name to get user IDs from.
+ * @return {string[]} An array of user IDs or an empty array.
+ */
 RoomState.prototype.getUserIdsWithDisplayName = function(displayName) {
     return this._displayNameToUserIds[displayName] || [];
 };