diff --git a/lib/client.js b/lib/client.js
index c257edffb..232b2f19b 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -80,8 +80,12 @@ var DeviceVerification = {
  * @param {Object=} opts.store The data store to use. If not specified,
  * this client will not store any HTTP responses.
  *
- * @param {string=} opts.deviceId A unique identifier for this device, for use
- *    in end-to-end crypto. If not specified, end-to-end crypto will be disabled.
+ * @param {string=} opts.deviceId A unique identifier for this device; used for
+ *    tracking things like crypto keys and access tokens.  If not specified,
+ *    end-to-end crypto will be disabled.
+ *
+ * @param {string=} opts.defaultDeviceDisplayName Initial display name to set
+ *    on new devices
  *
  * @param {Object=} opts.sessionStore A store to be used for end-to-end crypto
  *    session data. This should be a {@link
@@ -115,9 +119,16 @@ function MatrixClient(opts) {
     this.sessionStore = opts.sessionStore || null;
 
     this.deviceId = opts.deviceId;
+    this.defaultDeviceDisplayName = opts.defaultDeviceDisplayName || "js-sdk device";
+
+    var userId = (opts.userId || null);
+    this.credentials = {
+        userId: userId,
+    };
+
     this._olmDevice = null;
 
-    if (CRYPTO_ENABLED && this.sessionStore !== null) {
+    if (CRYPTO_ENABLED && this.sessionStore !== null && userId !== null) {
         this._olmDevice = new OlmDevice(opts.sessionStore);
 
         var json = '{"algorithms":["' + OLM_ALGORITHM + '"]';
@@ -128,13 +139,13 @@ function MatrixClient(opts) {
         json += ',"curve25519:' + this.deviceId + '":';
         json += JSON.stringify(this._olmDevice.deviceCurve25519Key);
         json += '}';
-        json += ',"user_id":' + JSON.stringify(opts.userId);
+        json += ',"user_id":' + JSON.stringify(userId);
         json += '}';
         var signature = this._olmDevice.sign(json);
         this.deviceKeys = JSON.parse(json);
         var signatures = {};
-        signatures[opts.userId] = {};
-        signatures[opts.userId]["ed25519:" + this.deviceId] = signature;
+        signatures[userId] = {};
+        signatures[userId]["ed25519:" + this.deviceId] = signature;
         this.deviceKeys.signatures = signatures;
 
         var deviceInfo = {
@@ -143,11 +154,11 @@ function MatrixClient(opts) {
             verified: DeviceVerification.VERIFIED,
         };
         var myDevices = this.sessionStore.getEndToEndDevicesForUser(
-            opts.userId
+            userId
         ) || {};
         myDevices[opts.deviceId] = deviceInfo;
         this.sessionStore.storeEndToEndDevicesForUser(
-            opts.userId, myDevices
+            userId, myDevices
         );
         setupCryptoEventHandler(this);
     }
@@ -174,9 +185,6 @@ function MatrixClient(opts) {
         onlyData: true,
         extraParams: opts.queryParams
     };
-    this.credentials = {
-        userId: (opts.userId || null)
-    };
     this._http = new httpApi.MatrixHttpApi(this, httpOpts);
     this.callList = {
         // callId: MatrixCall
@@ -2689,9 +2697,19 @@ MatrixClient.prototype.paginateEventTimeline = function(eventTimeline, opts) {
  * @return {module:http-api.MatrixError} Rejects: with an error response.
  */
 MatrixClient.prototype.login = function(loginType, data, callback) {
-    data.type = loginType;
+    var login_data = {
+        type: loginType,
+        device_id: this.deviceId,
+        initial_device_display_name: this.defaultDeviceDisplayName,
+    };
+
+    // merge data into login_data
+    for (var k in data) {
+        if (data.hasOwnProperty(k)) { login_data[k] = data[k]; }
+    }
+
     return this._http.authedRequest(
-        callback, "POST", "/login", undefined, data
+        callback, "POST", "/login", undefined, login_data
     );
 };
 
@@ -2706,13 +2724,7 @@ MatrixClient.prototype.login = function(loginType, data, callback) {
 MatrixClient.prototype.registerGuest = function(opts, callback) {
     opts = opts || {};
     opts.body = opts.body || {};
-
-    return this._http.request(
-        callback, "POST", "/register", {
-            kind: "guest"
-        },
-        opts.body
-    );
+    return this.registerRequest(opts.body, "guest", callback);
 };
 
 /**
@@ -2793,9 +2805,33 @@ MatrixClient.prototype.register = function(username, password,
     if (bindEmail !== undefined) { params.bind_email = bindEmail; }
     if (guestAccessToken !== undefined) { params.guest_access_token = guestAccessToken; }
 
+    return this.registerRequest(params, undefined, callback);
+};
+
+
+/**
+ * @param {Object} data   parameters for registration request
+ * @param {string=} kind  type of user to register. may be "guest"
+ * @param {module:client.callback=} callback
+ * @return {module:client.Promise} Resolves: to the /register response
+ * @return {module:http-api.MatrixError} Rejects: with an error response.
+ */
+MatrixClient.prototype.registerRequest = function(data, kind, callback) {
+    var request_data = {
+        device_id: this.deviceId,
+        initial_device_display_name: this.defaultDeviceDisplayName,
+    };
+
+    // merge data into request_data
+    for (var k in data) {
+        if (data.hasOwnProperty(k)) { request_data[k] = data[k]; }
+    }
+
+    var params = {};
+    if (kind) { params.kind = kind; }
+
     return this._http.request(
-        callback, "POST", "/register", undefined,
-        params
+        callback, "POST", "/register", params, request_data
     );
 };