diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index 8b91462dd3cc..23fdebff6c66 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -7656,8 +7656,9 @@ var Distribution = {
     }
 
     // Apply a lightweight theme if necessary
-    if (prefs["lightweightThemes.isThemeSelected"])
+    if (prefs && prefs["lightweightThemes.isThemeSelected"]) {
       Services.obs.notifyObservers(null, "lightweight-theme-apply", "");
+    }
 
     let localizedString = Cc["@mozilla.org/pref-localizedstring;1"].createInstance(Ci.nsIPrefLocalizedString);
     let localizeablePrefs = aData["LocalizablePreferences"];