diff --git a/kivmob.py b/kivmob.py
index 09704e5..43ff3ad 100644
--- a/kivmob.py
+++ b/kivmob.py
@@ -213,6 +213,7 @@ def on_rewarded_video_ad_completed(self):
 
 
 class AndroidBridge(AdMobBridge):
+    _test_devices = []
     @run_on_ui_thread
     def __init__(self, appID):
         self._loaded = False
@@ -228,7 +229,6 @@ def __init__(self, appID):
         self._rewarded = MobileAds.getRewardedVideoAdInstance(
             activity.mActivity
         )
-        self._test_devices = []
 
     @run_on_ui_thread
     def add_test_device(self, testID):