diff --git a/lib/DbusInterfaceBase.js b/lib/DbusInterfaceBase.js
index 9c87a8c..7bb9a54 100644
--- a/lib/DbusInterfaceBase.js
+++ b/lib/DbusInterfaceBase.js
@@ -5,6 +5,7 @@ class DbusInterfaceBase extends EventEmitter {
         super();
         this._interface = interface_;
         this._bluez = bluez;
+        this._propertyInterface = null;
 
         // forward property change events
         const forwardPropertyChange = (iface, changed, invalidated) => {
@@ -77,4 +78,4 @@ class DbusInterfaceBase extends EventEmitter {
 
 }
 
-module.exports = DbusInterfaceBase;
\ No newline at end of file
+module.exports = DbusInterfaceBase;