diff --git a/src/scheduler.js b/src/scheduler.js
index c591af754..59611ff62 100644
--- a/src/scheduler.js
+++ b/src/scheduler.js
@@ -66,7 +66,7 @@ function sync(callback) {
                     return iteratorDone(); // nothing changed
                 }
 
-                var killContainers = appState && !appState.cronJobs; // keep the old containers on 'startup'
+                var killContainers = appState && !appState.cronJobs ? true : false; // keep the old containers on 'startup'
                 stopJobs(app.id, appState, killContainers, function (error) {
                     if (error) debug('Error stopping jobs for %s : %s', app.id, error.message);
 
@@ -107,8 +107,9 @@ function killContainer(containerId, callback) {
 
 function stopJobs(appId, appState, killContainers, callback) {
     assert.strictEqual(typeof appId, 'string');
-    assert.strictEqual(typeof killContainers, 'boolean');
     assert.strictEqual(typeof appState, 'object');
+    assert.strictEqual(typeof killContainers, 'boolean');
+    assert.strictEqual(typeof callback, 'function');
 
     debug('stopJobs for %s', appId);