diff --git a/src/apptask.js b/src/apptask.js
index 6fac200a5..e60267e63 100644
--- a/src/apptask.js
+++ b/src/apptask.js
@@ -64,6 +64,9 @@ function debugApp(app) {
 }
 
 function makeTaskError(error, app) {
+    assert.strictEqual(typeof error, 'object');
+    assert.strictEqual(typeof app, 'object');
+
     // track a few variables which helps 'repair' restart the task (see also scheduleTask in apps.js)
     error.details.taskId = app.taskId;
     error.details.installationState = app.installationState;