diff --git a/src/PepperDash.Essentials.Devices.Common/AudioCodec/Interfaces/IDtmfDecode.cs b/src/PepperDash.Essentials.Devices.Common/AudioCodec/Interfaces/IDtmfDecode.cs
index 27f8ee3a..a161a3d1 100644
--- a/src/PepperDash.Essentials.Devices.Common/AudioCodec/Interfaces/IDtmfDecode.cs
+++ b/src/PepperDash.Essentials.Devices.Common/AudioCodec/Interfaces/IDtmfDecode.cs
@@ -1,3 +1,4 @@
+using System;
 namespace PepperDash.Essentials.Devices.Common.AudioCodec;
 
 /// <summary>