diff --git a/dlls/d3d10core/buffer.c b/dlls/d3d10core/buffer.c
index fd2175e9a12..90ff0e8a5d0 100644
--- a/dlls/d3d10core/buffer.c
+++ b/dlls/d3d10core/buffer.c
@@ -24,11 +24,16 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(d3d10core);
 
+static inline struct d3d10_buffer *impl_from_ID3D10Buffer(ID3D10Buffer *iface)
+{
+    return CONTAINING_RECORD(iface, struct d3d10_buffer, ID3D10Buffer_iface);
+}
+
 /* IUnknown methods */
 
-static HRESULT STDMETHODCALLTYPE d3d10_buffer_QueryInterface(ID3D10Buffer *iface, REFIID riid, void **object)
+static HRESULT STDMETHODCALLTYPE d3d10_buffer_QueryInterface(ID3D10Buffer *iface, REFIID riid, void **out)
 {
-    TRACE("iface %p, riid %s, object %p\n", iface, debugstr_guid(riid), object);
+    TRACE("iface %p, riid %s, out %p.\n", iface, debugstr_guid(riid), out);
 
     if (IsEqualGUID(riid, &IID_ID3D10Buffer)
             || IsEqualGUID(riid, &IID_ID3D10Resource)
@@ -36,40 +41,38 @@ static HRESULT STDMETHODCALLTYPE d3d10_buffer_QueryInterface(ID3D10Buffer *iface
             || IsEqualGUID(riid, &IID_IUnknown))
     {
         IUnknown_AddRef(iface);
-        *object = iface;
+        *out = iface;
         return S_OK;
     }
 
     WARN("%s not implemented, returning E_NOINTERFACE\n", debugstr_guid(riid));
 
-    *object = NULL;
+    *out = NULL;
     return E_NOINTERFACE;
 }
 
 static ULONG STDMETHODCALLTYPE d3d10_buffer_AddRef(ID3D10Buffer *iface)
 {
-    struct d3d10_buffer *This = (struct d3d10_buffer *)iface;
-    ULONG refcount = InterlockedIncrement(&This->refcount);
+    struct d3d10_buffer *buffer = impl_from_ID3D10Buffer(iface);
+    ULONG refcount = InterlockedIncrement(&buffer->refcount);
 
-    TRACE("%p increasing refcount to %u\n", This, refcount);
+    TRACE("%p increasing refcount to %u.\n", buffer, refcount);
 
     if (refcount == 1)
-        wined3d_buffer_incref(This->wined3d_buffer);
+        wined3d_buffer_incref(buffer->wined3d_buffer);
 
     return refcount;
 }
 
 static ULONG STDMETHODCALLTYPE d3d10_buffer_Release(ID3D10Buffer *iface)
 {
-    struct d3d10_buffer *This = (struct d3d10_buffer *)iface;
-    ULONG refcount = InterlockedDecrement(&This->refcount);
+    struct d3d10_buffer *buffer = impl_from_ID3D10Buffer(iface);
+    ULONG refcount = InterlockedDecrement(&buffer->refcount);
 
-    TRACE("%p decreasing refcount to %u\n", This, refcount);
+    TRACE("%p decreasing refcount to %u.\n", buffer, refcount);
 
     if (!refcount)
-    {
-        wined3d_buffer_decref(This->wined3d_buffer);
-    }
+        wined3d_buffer_decref(buffer->wined3d_buffer);
 
     return refcount;
 }
@@ -132,7 +135,7 @@ static UINT STDMETHODCALLTYPE d3d10_buffer_GetEvictionPriority(ID3D10Buffer *ifa
 
 static HRESULT STDMETHODCALLTYPE d3d10_buffer_Map(ID3D10Buffer *iface, D3D10_MAP map_type, UINT map_flags, void **data)
 {
-    struct d3d10_buffer *buffer = (struct d3d10_buffer *)iface;
+    struct d3d10_buffer *buffer = impl_from_ID3D10Buffer(iface);
 
     TRACE("iface %p, map_type %u, map_flags %#x, data %p.\n", iface, map_type, map_flags, data);
 
@@ -146,9 +149,11 @@ static HRESULT STDMETHODCALLTYPE d3d10_buffer_Map(ID3D10Buffer *iface, D3D10_MAP
 
 static void STDMETHODCALLTYPE d3d10_buffer_Unmap(ID3D10Buffer *iface)
 {
+    struct d3d10_buffer *buffer = impl_from_ID3D10Buffer(iface);
+
     TRACE("iface %p.\n", iface);
 
-    wined3d_buffer_unmap(((struct d3d10_buffer *)iface)->wined3d_buffer);
+    wined3d_buffer_unmap(buffer->wined3d_buffer);
 }
 
 static void STDMETHODCALLTYPE d3d10_buffer_GetDesc(ID3D10Buffer *iface, D3D10_BUFFER_DESC *desc)
@@ -177,6 +182,14 @@ static const struct ID3D10BufferVtbl d3d10_buffer_vtbl =
     d3d10_buffer_GetDesc,
 };
 
+struct d3d10_buffer *unsafe_impl_from_ID3D10Buffer(ID3D10Buffer *iface)
+{
+    if (!iface)
+        return NULL;
+    assert(iface->lpVtbl == &d3d10_buffer_vtbl);
+    return CONTAINING_RECORD(iface, struct d3d10_buffer, ID3D10Buffer_iface);
+}
+
 static void STDMETHODCALLTYPE d3d10_buffer_wined3d_object_released(void *parent)
 {
     HeapFree(GetProcessHeap(), 0, parent);
@@ -193,7 +206,7 @@ HRESULT d3d10_buffer_init(struct d3d10_buffer *buffer, struct d3d10_device *devi
     struct wined3d_buffer_desc wined3d_desc;
     HRESULT hr;
 
-    buffer->vtbl = &d3d10_buffer_vtbl;
+    buffer->ID3D10Buffer_iface.lpVtbl = &d3d10_buffer_vtbl;
     buffer->refcount = 1;
 
     FIXME("Implement DXGI<->wined3d usage conversion\n");
diff --git a/dlls/d3d10core/d3d10core_private.h b/dlls/d3d10core/d3d10core_private.h
index d99a337053f..5f320e01c1b 100644
--- a/dlls/d3d10core/d3d10core_private.h
+++ b/dlls/d3d10core/d3d10core_private.h
@@ -21,6 +21,8 @@
 
 #include "wine/debug.h"
 
+#include <assert.h>
+
 #define COBJMACROS
 #include "winbase.h"
 #include "wingdi.h"
@@ -111,7 +113,7 @@ HRESULT d3d10_texture3d_init(struct d3d10_texture3d *texture, struct d3d10_devic
 /* ID3D10Buffer */
 struct d3d10_buffer
 {
-    const struct ID3D10BufferVtbl *vtbl;
+    ID3D10Buffer ID3D10Buffer_iface;
     LONG refcount;
 
     struct wined3d_buffer *wined3d_buffer;
@@ -119,6 +121,7 @@ struct d3d10_buffer
 
 HRESULT d3d10_buffer_init(struct d3d10_buffer *buffer, struct d3d10_device *device,
         const D3D10_BUFFER_DESC *desc, const D3D10_SUBRESOURCE_DATA *data) DECLSPEC_HIDDEN;
+struct d3d10_buffer *unsafe_impl_from_ID3D10Buffer(ID3D10Buffer *iface) DECLSPEC_HIDDEN;
 
 /* ID3D10DepthStencilView */
 struct d3d10_depthstencil_view
diff --git a/dlls/d3d10core/device.c b/dlls/d3d10core/device.c
index cf21bba834f..637109f14df 100644
--- a/dlls/d3d10core/device.c
+++ b/dlls/d3d10core/device.c
@@ -203,9 +203,10 @@ static void STDMETHODCALLTYPE d3d10_device_IASetVertexBuffers(ID3D10Device *ifac
 
     for (i = 0; i < buffer_count; ++i)
     {
+        struct d3d10_buffer *buffer = unsafe_impl_from_ID3D10Buffer(buffers[i]);
+
         wined3d_device_set_stream_source(This->wined3d_device, start_slot,
-                buffers[i] ? ((struct d3d10_buffer *)buffers[i])->wined3d_buffer : NULL,
-                offsets[i], strides[i]);
+                buffer ? buffer->wined3d_buffer : NULL, offsets[i], strides[i]);
     }
 }
 
@@ -213,12 +214,13 @@ static void STDMETHODCALLTYPE d3d10_device_IASetIndexBuffer(ID3D10Device *iface,
         ID3D10Buffer *buffer, DXGI_FORMAT format, UINT offset)
 {
     struct d3d10_device *This = impl_from_ID3D10Device(iface);
+    struct d3d10_buffer *buffer_impl = unsafe_impl_from_ID3D10Buffer(buffer);
 
     TRACE("iface %p, buffer %p, format %s, offset %u.\n",
             iface, buffer, debug_dxgi_format(format), offset);
 
     wined3d_device_set_index_buffer(This->wined3d_device,
-            buffer ? ((struct d3d10_buffer *)buffer)->wined3d_buffer : NULL,
+            buffer_impl ? buffer_impl->wined3d_buffer : NULL,
             wined3dformat_from_dxgi_format(format));
     if (offset) FIXME("offset %u not supported.\n", offset);
 }
@@ -644,7 +646,7 @@ static HRESULT STDMETHODCALLTYPE d3d10_device_CreateBuffer(ID3D10Device *iface,
         return hr;
     }
 
-    *buffer = (ID3D10Buffer *)object;
+    *buffer = &object->ID3D10Buffer_iface;
 
     TRACE("Created ID3D10Buffer %p\n", object);
 
diff --git a/dlls/d3d10core/inputlayout.c b/dlls/d3d10core/inputlayout.c
index d6ae787f113..09b8998df84 100644
--- a/dlls/d3d10core/inputlayout.c
+++ b/dlls/d3d10core/inputlayout.c
@@ -19,7 +19,6 @@
 
 #include "config.h"
 #include "wine/port.h"
-#include <assert.h>
 
 #include "d3d10core_private.h"
 
diff --git a/dlls/d3d10core/shader.c b/dlls/d3d10core/shader.c
index 82ddadc4980..c6803ed3752 100644
--- a/dlls/d3d10core/shader.c
+++ b/dlls/d3d10core/shader.c
@@ -19,7 +19,6 @@
 
 #include "config.h"
 #include "wine/port.h"
-#include <assert.h>
 
 #include "d3d10core_private.h"
 
diff --git a/dlls/d3d10core/view.c b/dlls/d3d10core/view.c
index 57c4148e63d..57473e4ae11 100644
--- a/dlls/d3d10core/view.c
+++ b/dlls/d3d10core/view.c
@@ -19,7 +19,6 @@
 
 #include "config.h"
 #include "wine/port.h"
-#include <assert.h>
 
 #define NONAMELESSUNION
 #include "d3d10core_private.h"