diff --git a/miniwin/include/miniwin/d3drm.h b/miniwin/include/miniwin/d3drm.h
index dea6e0f7..365046a5 100644
--- a/miniwin/include/miniwin/d3drm.h
+++ b/miniwin/include/miniwin/d3drm.h
@@ -181,10 +181,10 @@ struct IDirect3DRMMesh : public IDirect3DRMVisual {
 	virtual HRESULT Clone(int flags, GUID iid, void** object) = 0;
 	virtual HRESULT GetBox(D3DRMBOX* box) = 0;
 	virtual HRESULT AddGroup(
-		unsigned int vertexCount,
-		unsigned int faceCount,
-		unsigned int vertexPerFace,
-		unsigned int* faceBuffer,
+		int vertexCount,
+		int faceCount,
+		int vertexPerFace,
+		DWORD* faceBuffer,
 		D3DRMGROUPINDEX* groupIndex
 	) = 0;
 	virtual HRESULT GetGroup(
diff --git a/miniwin/src/d3drm/d3drmmesh.cpp b/miniwin/src/d3drm/d3drmmesh.cpp
index 5d96ac86..dc8c8686 100644
--- a/miniwin/src/d3drm/d3drmmesh.cpp
+++ b/miniwin/src/d3drm/d3drmmesh.cpp
@@ -40,10 +40,10 @@ HRESULT Direct3DRMMeshImpl::Clone(int flags, GUID iid, void** object)
 }
 
 HRESULT Direct3DRMMeshImpl::AddGroup(
-	unsigned int vertexCount,
-	unsigned int faceCount,
-	unsigned int vertexPerFace,
-	unsigned int* faceBuffer,
+	int vertexCount,
+	int faceCount,
+	int vertexPerFace,
+	DWORD* faceBuffer,
 	D3DRMGROUPINDEX* groupIndex
 )
 {
diff --git a/miniwin/src/internal/d3drmmesh_impl.h b/miniwin/src/internal/d3drmmesh_impl.h
index e06192e4..ca72dbc6 100644
--- a/miniwin/src/internal/d3drmmesh_impl.h
+++ b/miniwin/src/internal/d3drmmesh_impl.h
@@ -67,13 +67,8 @@ struct MeshGroup {
 struct Direct3DRMMeshImpl : public Direct3DRMObjectBaseImpl<IDirect3DRMMesh> {
 	HRESULT QueryInterface(const GUID& riid, void** ppvObject) override;
 	HRESULT Clone(int flags, GUID iid, void** object) override;
-	HRESULT AddGroup(
-		unsigned int vertexCount,
-		unsigned int faceCount,
-		unsigned int vertexPerFace,
-		unsigned int* faceBuffer,
-		D3DRMGROUPINDEX* groupIndex
-	) override;
+	HRESULT AddGroup(int vertexCount, int faceCount, int vertexPerFace, DWORD* faceBuffer, D3DRMGROUPINDEX* groupIndex)
+		override;
 	HRESULT GetGroup(
 		D3DRMGROUPINDEX groupIndex,
 		unsigned int* vertexCount,