diff --git a/dlls/dmcompos/dmcompos_private.h b/dlls/dmcompos/dmcompos_private.h
index 8e67a183274..a74c1fb880a 100644
--- a/dlls/dmcompos/dmcompos_private.h
+++ b/dlls/dmcompos/dmcompos_private.h
@@ -78,17 +78,9 @@ typedef struct {
 } guid_info;
 
 /* used for initialising structs (primarily for DMUS_OBJECTDESC) */
-#define DM_STRUCT_INIT(x) 				\
-	do {								\
-		memset((x), 0, sizeof(*(x)));	\
-		(x)->dwSize = sizeof(*x);		\
-	} while (0)
-
 #define FE(x) { x, #x }	
 #define GE(x) { &x, #x }
 
-#define ICOM_THIS_MULTI(impl,field,iface) impl* const This=(impl*)((char*)(iface) - offsetof(impl,field))
-
 /* FOURCC to string conversion for debug messages */
 extern const char *debugstr_fourcc (DWORD fourcc) DECLSPEC_HIDDEN;
 /* returns name of given GUID */
diff --git a/dlls/dmcompos/signposttrack.c b/dlls/dmcompos/signposttrack.c
index e91f7bb0e90..2b4712bd644 100644
--- a/dlls/dmcompos/signposttrack.c
+++ b/dlls/dmcompos/signposttrack.c
@@ -18,6 +18,7 @@
  */
 
 #include "dmcompos_private.h"
+#include "dmobject.h"
 
 WINE_DEFAULT_DEBUG_CHANNEL(dmcompos);
 
@@ -26,9 +27,8 @@ WINE_DEFAULT_DEBUG_CHANNEL(dmcompos);
  */
 typedef struct IDirectMusicSignPostTrack {
     IDirectMusicTrack8 IDirectMusicTrack8_iface;
-    const IPersistStreamVtbl *PersistStreamVtbl;
+    struct dmobject dmobj;  /* IPersistStream only */
     LONG ref;
-    DMUS_OBJECTDESC *pDesc;
 } IDirectMusicSignPostTrack;
 
 /* IDirectMusicSignPostTrack IDirectMusicTrack8 part: */
@@ -50,7 +50,7 @@ static HRESULT WINAPI IDirectMusicTrack8Impl_QueryInterface(IDirectMusicTrack8 *
             IsEqualIID(riid, &IID_IDirectMusicTrack8))
         *ret_iface = iface;
     else if (IsEqualIID(riid, &IID_IPersistStream))
-        *ret_iface = &This->PersistStreamVtbl;
+        *ret_iface = &This->dmobj.IPersistStream_iface;
     else {
         WARN("(%p, %s, %p): not found\n", This, debugstr_dmguid(riid), ret_iface);
         return E_NOINTERFACE;
@@ -238,54 +238,33 @@ static const IDirectMusicTrack8Vtbl dmtrack8_vtbl = {
     IDirectMusicTrack8Impl_Join
 };
 
-/* IDirectMusicSignPostTrack IPersistStream part: */
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_QueryInterface (LPPERSISTSTREAM iface, REFIID riid, LPVOID *ppobj) {
-	ICOM_THIS_MULTI(IDirectMusicSignPostTrack, PersistStreamVtbl, iface);
-	return IDirectMusicTrack8_QueryInterface(&This->IDirectMusicTrack8_iface, riid, ppobj);
+static inline IDirectMusicSignPostTrack * impl_from_IPersistStream(IPersistStream *iface)
+{
+    return CONTAINING_RECORD(iface, IDirectMusicSignPostTrack, dmobj.IPersistStream_iface);
 }
 
-static ULONG WINAPI IDirectMusicSignPostTrack_IPersistStream_AddRef (LPPERSISTSTREAM iface) {
-	ICOM_THIS_MULTI(IDirectMusicSignPostTrack, PersistStreamVtbl, iface);
-	return IDirectMusicTrack8_AddRef(&This->IDirectMusicTrack8_iface);
-}
-
-static ULONG WINAPI IDirectMusicSignPostTrack_IPersistStream_Release (LPPERSISTSTREAM iface) {
-	ICOM_THIS_MULTI(IDirectMusicSignPostTrack, PersistStreamVtbl, iface);
-	return IDirectMusicTrack8_Release(&This->IDirectMusicTrack8_iface);
-}
-
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_GetClassID (LPPERSISTSTREAM iface, CLSID* pClassID) {
-	return E_NOTIMPL;
-}
-
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_IsDirty (LPPERSISTSTREAM iface) {
-	return E_NOTIMPL;
-}
-
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_Load (LPPERSISTSTREAM iface, IStream* pStm) {
-	ICOM_THIS_MULTI(IDirectMusicSignPostTrack, PersistStreamVtbl, iface);
+static HRESULT WINAPI IPersistStreamImpl_Load(IPersistStream *iface, IStream *pStm)
+{
+        IDirectMusicSignPostTrack *This = impl_from_IPersistStream(iface);
 	FIXME("(%p, %p): Loading not implemented yet\n", This, pStm);
 	return S_OK;
 }
 
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_Save (LPPERSISTSTREAM iface, IStream* pStm, BOOL fClearDirty) {
-	return E_NOTIMPL;
-}
-
-static HRESULT WINAPI IDirectMusicSignPostTrack_IPersistStream_GetSizeMax (LPPERSISTSTREAM iface, ULARGE_INTEGER* pcbSize) {
-	return E_NOTIMPL;
-}
-
-static const IPersistStreamVtbl DirectMusicSignPostTrack_PersistStream_Vtbl =
+static HRESULT WINAPI IPersistStreamImpl_Save(IPersistStream *iface, IStream *stream,
+        BOOL cleardirty)
 {
-	IDirectMusicSignPostTrack_IPersistStream_QueryInterface,
-	IDirectMusicSignPostTrack_IPersistStream_AddRef,
-	IDirectMusicSignPostTrack_IPersistStream_Release,
-	IDirectMusicSignPostTrack_IPersistStream_GetClassID,
-	IDirectMusicSignPostTrack_IPersistStream_IsDirty,
-	IDirectMusicSignPostTrack_IPersistStream_Load,
-	IDirectMusicSignPostTrack_IPersistStream_Save,
-	IDirectMusicSignPostTrack_IPersistStream_GetSizeMax
+	return E_NOTIMPL;
+}
+
+static const IPersistStreamVtbl persiststream_vtbl = {
+    dmobj_IPersistStream_QueryInterface,
+    dmobj_IPersistStream_AddRef,
+    dmobj_IPersistStream_Release,
+    dmobj_IPersistStream_GetClassID,
+    unimpl_IPersistStream_IsDirty,
+    IPersistStreamImpl_Load,
+    IPersistStreamImpl_Save,
+    unimpl_IPersistStream_GetSizeMax
 };
 
 /* for ClassFactory */
@@ -300,12 +279,10 @@ HRESULT WINAPI create_dmsignposttrack(REFIID lpcGUID, void **ppobj)
         return E_OUTOFMEMORY;
     }
     track->IDirectMusicTrack8_iface.lpVtbl = &dmtrack8_vtbl;
-	track->PersistStreamVtbl = &DirectMusicSignPostTrack_PersistStream_Vtbl;
-	track->pDesc = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(DMUS_OBJECTDESC));
-	DM_STRUCT_INIT(track->pDesc);
-	track->pDesc->dwValidData |= DMUS_OBJ_CLASS;
-	track->pDesc->guidClass = CLSID_DirectMusicSignPostTrack;
     track->ref = 1;
+    dmobject_init(&track->dmobj, &CLSID_DirectMusicSignPostTrack,
+                  (IUnknown *)&track->IDirectMusicTrack8_iface);
+    track->dmobj.IPersistStream_iface.lpVtbl = &persiststream_vtbl;
 
     DMCOMPOS_LockModule();
     hr = IDirectMusicTrack8_QueryInterface(&track->IDirectMusicTrack8_iface, lpcGUID, ppobj);
diff --git a/dlls/dmcompos/tests/dmcompos.c b/dlls/dmcompos/tests/dmcompos.c
index 0ca559973e9..6d81145df02 100644
--- a/dlls/dmcompos/tests/dmcompos.c
+++ b/dlls/dmcompos/tests/dmcompos.c
@@ -383,15 +383,15 @@ static void test_signposttrack(void)
     hr = IDirectMusicTrack8_QueryInterface(dmt8, &IID_IPersistStream, (void**)&ps);
     ok(hr == S_OK, "QueryInterface for IID_IPersistStream failed: %08x\n", hr);
     hr = IPersistStream_GetClassID(ps, &class);
-    todo_wine ok(hr == S_OK, "IPersistStream_GetClassID failed: %08x\n", hr);
-    todo_wine ok(IsEqualGUID(&class, &CLSID_DirectMusicSignPostTrack),
+    ok(hr == S_OK, "IPersistStream_GetClassID failed: %08x\n", hr);
+    ok(IsEqualGUID(&class, &CLSID_DirectMusicSignPostTrack),
             "Expected class CLSID_DirectMusicSignPostTrack got %s\n", wine_dbgstr_guid(&class));
     hr = IPersistStream_Save(ps, NULL, TRUE);
     todo_wine ok(hr == E_POINTER, "IPersistStream_Save failed: %08x\n", hr);
 
     /* Unimplemented IPersistStream methods */
     hr = IPersistStream_IsDirty(ps);
-    todo_wine ok(hr == S_FALSE, "IPersistStream_IsDirty failed: %08x\n", hr);
+    ok(hr == S_FALSE, "IPersistStream_IsDirty failed: %08x\n", hr);
     hr = IPersistStream_GetSizeMax(ps, &size);
     ok(hr == E_NOTIMPL, "IPersistStream_GetSizeMax failed: %08x\n", hr);