diff --git a/src/client.js b/src/client.js
index 22a88e6ac..ae6c4fe1a 100644
--- a/src/client.js
+++ b/src/client.js
@@ -590,14 +590,13 @@ MatrixClient.prototype.isEventSenderVerified = async function(event) {
  * Enable end-to-end encryption for a room.
  * @param {string} roomId The room ID to enable encryption in.
  * @param {object} config The encryption config for the room.
- * @return {Object} A promise that will resolve when encryption is setup.
+ * @return {Promise} A promise that will resolve when encryption is set up.
  */
 MatrixClient.prototype.setRoomEncryption = function(roomId, config) {
     if (!this._crypto) {
         throw new Error("End-to-End encryption disabled");
     }
-    this._crypto.setRoomEncryption(roomId, config);
-    return Promise.resolve();
+    return this._crypto.setRoomEncryption(roomId, config);
 };
 
 /**
diff --git a/src/crypto/index.js b/src/crypto/index.js
index 9847f0f24..0bc6533d3 100644
--- a/src/crypto/index.js
+++ b/src/crypto/index.js
@@ -580,7 +580,7 @@ Crypto.prototype.getEventSenderDeviceInfo = function(event) {
  * @param {boolean=} inhibitDeviceQuery true to suppress device list query for
  *   users in the room (for now)
  */
-Crypto.prototype.setRoomEncryption = function(roomId, config, inhibitDeviceQuery) {
+Crypto.prototype.setRoomEncryption = async function(roomId, config, inhibitDeviceQuery) {
     // if we already have encryption in this room, we should ignore this event
     // (for now at least. maybe we should alert the user somehow?)
     const existingConfig = this._sessionStore.getEndToEndRoom(roomId);
@@ -842,7 +842,7 @@ Crypto.prototype.onCryptoEvent = async function(event) {
     try {
         // inhibit the device list refresh for now - it will happen once we've
         // finished processing the sync, in _onSyncCompleted.
-        this.setRoomEncryption(roomId, content, true);
+        await this.setRoomEncryption(roomId, content, true);
     } catch (e) {
         console.error("Error configuring encryption in room " + roomId +
                       ":", e);