diff --git a/drivers/wdm/audio/backpln/portcls/interfaces.hpp b/drivers/wdm/audio/backpln/portcls/interfaces.hpp
index 730b6a3adfb..dc030ed1168 100644
--- a/drivers/wdm/audio/backpln/portcls/interfaces.hpp
+++ b/drivers/wdm/audio/backpln/portcls/interfaces.hpp
@@ -354,7 +354,7 @@ DECLARE_INTERFACE_(IIrpQueue, IUnknown)
 
     STDMETHOD_(BOOLEAN, GetAcquiredTagRange)(THIS_
         IN PVOID * FirstTag,
-        IN PVOID * LastTag);
+        IN PVOID * LastTag) PURE;
 
 };