diff --git a/dlls/dpnet/dpnet_private.h b/dlls/dpnet/dpnet_private.h
index 8207a67fa97..9254295794e 100644
--- a/dlls/dpnet/dpnet_private.h
+++ b/dlls/dpnet/dpnet_private.h
@@ -93,9 +93,8 @@ struct IDirectPlay8PeerImpl
  */
 struct IDirectPlay8ThreadPoolImpl
 {
-  /* IUnknown fields */
-  const IDirectPlay8ThreadPoolVtbl *lpVtbl;
-  LONG          ref;
+  IDirectPlay8ThreadPool IDirectPlay8ThreadPool_iface;
+  LONG ref;
 };
 
 /**
diff --git a/dlls/dpnet/threadpool.c b/dlls/dpnet/threadpool.c
index f94a3fa194e..274789d28b6 100644
--- a/dlls/dpnet/threadpool.c
+++ b/dlls/dpnet/threadpool.c
@@ -37,11 +37,16 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(dpnet);
 
-/* IUnknown interface follows */
-
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_QueryInterface(PDIRECTPLAY8THREADPOOL iface, REFIID riid, LPVOID *ppobj)
+static inline IDirectPlay8ThreadPoolImpl *impl_from_IDirectPlay8ThreadPool(IDirectPlay8ThreadPool *iface)
 {
-    IDirectPlay8ThreadPoolImpl *This = (IDirectPlay8ThreadPoolImpl*)iface;
+    return CONTAINING_RECORD(iface, IDirectPlay8ThreadPoolImpl, IDirectPlay8ThreadPool_iface);
+}
+
+/* IUnknown interface follows */
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_QueryInterface(IDirectPlay8ThreadPool *iface,
+        REFIID riid, void **ppobj)
+{
+    IDirectPlay8ThreadPoolImpl *This = impl_from_IDirectPlay8ThreadPool(iface);
 
     if(IsEqualGUID(riid, &IID_IUnknown) ||
        IsEqualGUID(riid, &IID_IDirectPlay8ThreadPool))
@@ -55,17 +60,17 @@ static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_QueryInterface(PDIRECTPLAY8THRE
     return E_NOINTERFACE;
 }
 
-static ULONG WINAPI IDirectPlay8ThreadPoolImpl_AddRef(PDIRECTPLAY8THREADPOOL iface)
+static ULONG WINAPI IDirectPlay8ThreadPoolImpl_AddRef(IDirectPlay8ThreadPool *iface)
 {
-    IDirectPlay8ThreadPoolImpl* This = (IDirectPlay8ThreadPoolImpl*)iface;
+    IDirectPlay8ThreadPoolImpl* This = impl_from_IDirectPlay8ThreadPool(iface);
     ULONG RefCount = InterlockedIncrement(&This->ref);
 
     return RefCount;
 }
 
-static ULONG WINAPI IDirectPlay8ThreadPoolImpl_Release(PDIRECTPLAY8THREADPOOL iface)
+static ULONG WINAPI IDirectPlay8ThreadPoolImpl_Release(IDirectPlay8ThreadPool *iface)
 {
-    IDirectPlay8ThreadPoolImpl* This = (IDirectPlay8ThreadPoolImpl*)iface;
+    IDirectPlay8ThreadPoolImpl* This = impl_from_IDirectPlay8ThreadPool(iface);
     ULONG RefCount = InterlockedDecrement(&This->ref);
 
     if(!RefCount)
@@ -75,31 +80,36 @@ static ULONG WINAPI IDirectPlay8ThreadPoolImpl_Release(PDIRECTPLAY8THREADPOOL if
 }
 
 /* IDirectPlay8ThreadPool interface follows */
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_Initialize(PDIRECTPLAY8THREADPOOL iface, PVOID CONST pvUserContext, CONST PFNDPNMESSAGEHANDLER pfn, CONST DWORD dwFlags)
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_Initialize(IDirectPlay8ThreadPool *iface,
+        void * const pvUserContext, const PFNDPNMESSAGEHANDLER pfn, const DWORD dwFlags)
 {
     FIXME("(%p)->(%p,%p,%x): stub\n", iface, pvUserContext, pfn, dwFlags);
     return DPN_OK;
 }
 
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_Close(PDIRECTPLAY8THREADPOOL iface, CONST DWORD dwFlags)
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_Close(IDirectPlay8ThreadPool *iface,
+        const DWORD dwFlags)
 {
     return DPN_OK;
 }
 
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_GetThreadCount(PDIRECTPLAY8THREADPOOL iface, CONST DWORD dwProcessorNum, DWORD* CONST pdwNumThreads, CONST DWORD dwFlags)
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_GetThreadCount(IDirectPlay8ThreadPool *iface,
+        const DWORD dwProcessorNum, DWORD * const pdwNumThreads, const DWORD dwFlags)
 {
     FIXME("(%p)->(%x,%p,%x): stub\n", iface, dwProcessorNum, pdwNumThreads, dwFlags);
     *pdwNumThreads = 0;
     return DPN_OK;
 }
 
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_SetThreadCount(PDIRECTPLAY8THREADPOOL iface, CONST DWORD dwProcessorNum, CONST DWORD dwNumThreads, CONST DWORD dwFlags)
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_SetThreadCount(IDirectPlay8ThreadPool *iface,
+        const DWORD dwProcessorNum, const DWORD dwNumThreads, const DWORD dwFlags)
 {
     FIXME("(%p)->(%x,%x,%x): stub\n", iface, dwProcessorNum, dwNumThreads, dwFlags);
     return DPN_OK;
 }
 
-static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_DoWork(PDIRECTPLAY8THREADPOOL iface, CONST DWORD dwAllowedTimeSlice, CONST DWORD dwFlags)
+static HRESULT WINAPI IDirectPlay8ThreadPoolImpl_DoWork(IDirectPlay8ThreadPool *iface,
+        const DWORD dwAllowedTimeSlice, const DWORD dwFlags)
 {
     static BOOL Run = FALSE;
 
@@ -136,8 +146,9 @@ HRESULT DPNET_CreateDirectPlay8ThreadPool(LPCLASSFACTORY iface, LPUNKNOWN punkOu
         return E_OUTOFMEMORY;
     }
 
-    Client->lpVtbl = &DirectPlay8ThreadPool_Vtbl;
+    Client->IDirectPlay8ThreadPool_iface.lpVtbl = &DirectPlay8ThreadPool_Vtbl;
     Client->ref = 0;
 
-    return IDirectPlay8ThreadPoolImpl_QueryInterface((PDIRECTPLAY8THREADPOOL)Client, riid, ppobj);
+    return IDirectPlay8ThreadPoolImpl_QueryInterface(&Client->IDirectPlay8ThreadPool_iface, riid,
+            ppobj);
 }