| Index: qunit/common.js | 
| diff --git a/qunit/common.js b/qunit/common.js | 
| index 8142b621d4e71d019239b964b1d52bb4fb6943d8..906348ce243b91729a5067c9dcfe1c47627fc0b4 100644 | 
| --- a/qunit/common.js | 
| +++ b/qunit/common.js | 
| @@ -15,6 +15,7 @@ | 
| * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>. | 
| */ | 
|  | 
| +"use strict"; | 
|  | 
| importAll("filterClasses", this); | 
| importAll("subscriptionClasses", this); | 
| @@ -43,9 +44,9 @@ function restoreFilterComponents() | 
| function preparePrefs() | 
| { | 
| this._pbackup = Object.create(null); | 
| -  for (var pref in Prefs) | 
| +  for (let pref in Prefs) | 
| { | 
| -    var value = Prefs[pref]; | 
| +    let value = Prefs[pref]; | 
| this._pbackup[pref] = value; | 
| } | 
| Prefs.enabled = true; | 
| @@ -53,7 +54,7 @@ function preparePrefs() | 
|  | 
| function restorePrefs() | 
| { | 
| -  for (var pref in this._pbackup) | 
| +  for (let pref in this._pbackup) | 
| Prefs[pref] = this._pbackup[pref]; | 
| } | 
|  | 
|  |