diff --git a/src/apps.js b/src/apps.js
index 9707d48a9..e3eb863e9 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -494,7 +494,7 @@ function update(appId, force, manifest, portBindings, icon, callback) {
     assert.strictEqual(typeof appId, 'string');
     assert.strictEqual(typeof force, 'boolean');
     assert(manifest && typeof manifest === 'object');
-    assert(!portBindings || typeof portBindings === 'object');
+    assert(typeof portBindings === 'object'); // can be null
     assert(!icon || typeof icon === 'string');
     assert.strictEqual(typeof callback, 'function');
 
diff --git a/src/routes/apps.js b/src/routes/apps.js
index b88488b55..587096fd8 100644
--- a/src/routes/apps.js
+++ b/src/routes/apps.js
@@ -274,7 +274,7 @@ function updateApp(req, res, next) {
 
     debug('Update app id:%s to manifest:%j with portBindings:%j', req.params.id, data.manifest, data.portBindings);
 
-    apps.update(req.params.id, data.force || false, data.manifest, data.portBindings, data.icon, function (error) {
+    apps.update(req.params.id, data.force || false, data.manifest, data.portBindings || null, data.icon, function (error) {
         if (error && error.reason === AppsError.NOT_FOUND) return next(new HttpError(404, 'No such app'));
         if (error && error.reason === AppsError.BAD_FIELD) return next(new HttpError(400, error.message));
         if (error && error.reason === AppsError.BAD_STATE) return next(new HttpError(409, error.message));