diff --git a/lib/client.js b/lib/client.js
index 3172a9f2b..2440ac44e 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -1946,6 +1946,34 @@ MatrixClient.prototype.setGuestRooms = function(roomIds) {
     this._guestRooms = roomIds;
 };
 
+/**
+ * Set r/w flags for guest access in a room.
+ * @param {string} roomId The room to configure guest access in.
+ * @param {Object} opts Options
+ * @param {boolean} opts.allowJoin True to allow guests to join this room. This
+ * implicitly gives guests write access. If false or not given, guests are
+ * explicitly forbidden from joining the room.
+ * @param {boolean} opts.allowRead True to set history visibility to
+ * be world_readable. This gives guests read access *from this point forward*.
+ * If false or not given, history visibility is not modified.
+ * @return {module:client.Promise} Resolves: TODO
+ * @return {module:http-api.MatrixError} Rejects: with an error response.
+ */
+MatrixClient.prototype.setGuestAccess = function(roomId, opts) {
+    var writePromise = this.sendStateEvent(roomId, "m.room.guest_access", {
+        guest_access: opts.allowJoin ? "can_join" : "forbidden"
+    });
+
+    var readPromise = q();
+    if (opts.allowRead) {
+        readPromise = this.sendStateEvent(roomId, "m.room.history_visibility", {
+            history_visibility: "world_readable"
+        });
+    }
+
+    return q.all(readPromise, writePromise);
+};
+
 /**
  * @param {string} username
  * @param {string} password
diff --git a/lib/sync.js b/lib/sync.js
index 10b68ffc4..58b4c3239 100644
--- a/lib/sync.js
+++ b/lib/sync.js
@@ -546,6 +546,9 @@ SyncApi.prototype._processRoomEvents = function(room, stateEventList,
     room.addEventsToTimeline(timelineEventList);
 };
 
+/**
+ * @return {string}
+ */
 SyncApi.prototype._getGuestFilter = function() {
     var guestRooms = this.client._guestRooms; // FIXME: horrible gut-wrenching
     if (!guestRooms) {