diff --git a/reactos/drivers/wdm/audio/backpln/portcls/interfaces.h b/reactos/drivers/wdm/audio/backpln/portcls/interfaces.h
index 66f5c4e7cea..d201e37cc6c 100644
--- a/reactos/drivers/wdm/audio/backpln/portcls/interfaces.h
+++ b/reactos/drivers/wdm/audio/backpln/portcls/interfaces.h
@@ -474,6 +474,8 @@ DECLARE_INTERFACE_(IPortPinWavePci, IIrpTarget)
 
 typedef IPortPinWavePci *PPORTPINWAVEPCI;
 
+#if (NTDDI_VERSION >= NTDDI_VISTA)
+
 /*****************************************************************************
  * IPortFilterWaveRT
  *****************************************************************************
@@ -518,6 +520,8 @@ DECLARE_INTERFACE_(IPortPinWaveRT, IIrpTarget)
 
 typedef IPortPinWavePci *PPORTPINWAVERT;
 
+#endif
+
 /*****************************************************************************
  * IPortFilterWaveCyclic
  *****************************************************************************
diff --git a/reactos/drivers/wdm/audio/backpln/portcls/private.h b/reactos/drivers/wdm/audio/backpln/portcls/private.h
index c974c740446..4667a6c126a 100644
--- a/reactos/drivers/wdm/audio/backpln/portcls/private.h
+++ b/reactos/drivers/wdm/audio/backpln/portcls/private.h
@@ -109,6 +109,8 @@ PMINIPORTWAVEPCI
 GetWavePciMiniport(
     PPORTWAVEPCI Port);
 
+#if (NTDDI_VERSION >= NTDDI_VISTA)
+
 NTSTATUS 
 NewPortFilterWaveRT(
     OUT IPortFilterWaveRT ** OutFilter);
@@ -128,6 +130,8 @@ NTSTATUS
 NewPortWaveRTStream(
     PPORTWAVERTSTREAM *OutStream);
 
+#endif
+
 NTSTATUS
 NTAPI
 NewDispatchObject(