--- a/mobile/android/tests/browser/robocop/src/org/mozilla/gecko/tests/SessionTest.java
+++ b/mobile/android/tests/browser/robocop/src/org/mozilla/gecko/tests/SessionTest.java
@@ -348,16 +348,17 @@ public abstract class SessionTest extend
     protected void verifySessionJSON(Session session, String sessionString, Assert asserter) {
         final SessionTab[] sessionTabs = session.getItems();
 
         try {
             final JSONObject window = new JSONObject(sessionString).getJSONArray("windows").getJSONObject(0);
             final JSONArray tabs = window.getJSONArray("tabs");
             final int optSelected = window.optInt("selected", -1);
 
+            asserter.is(tabs.length(), sessionTabs.length, "number of saved tabs matches");
             asserter.is(optSelected, session.getIndex() + 1, "selected tab matches");
 
             for (int i = 0; i < tabs.length(); i++) {
                 final JSONObject tab = tabs.getJSONObject(i);
                 final int index = tab.getInt("index");
                 final JSONArray entries = tab.getJSONArray("entries");
                 final SessionTab sessionTab = sessionTabs[i];
                 final PageInfo[] pages = sessionTab.getItems();