diff --git a/lib/accessories/alarmsensor.js b/lib/accessories/alarmsensor.js
index 822223b..c6c3451 100644
--- a/lib/accessories/alarmsensor.js
+++ b/lib/accessories/alarmsensor.js
@@ -55,7 +55,7 @@ FritzAlarmSensorAccessory.prototype.querySensorState = function() {
             : Characteristic.ContactSensorState.CONTACT_DETECTED;
 
         // invert if enabled
-        state = self.platform.deviceConfig(`${self.ain}.invert`, false)
+        state = this.platform.deviceConfig(`${this.ain}.invert`, false)
             ? 1-state
             : state;
 
diff --git a/package.json b/package.json
index 829b94f..053a24a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "homebridge-fritz",
-  "version": "0.9.3",
+  "version": "0.9.4",
   "author": "Andreas Goetz <cpuidle@gmx.de>",
   "homepage": "https://github.com/andig/homebridge-fritz#readme",
   "description": "Homebridge platform plugin for Fritz!Box",