diff --git a/src/renderer_d3d12.cpp b/src/renderer_d3d12.cpp
index 5b0e36ef4..86e2f820a 100644
--- a/src/renderer_d3d12.cpp
+++ b/src/renderer_d3d12.cpp
@@ -461,7 +461,7 @@ namespace bgfx { namespace d3d12
 			void* ptr;
 			DX_CHECK(resource->Map(0, NULL, &ptr) );
 			D3D12_RESOURCE_ALLOCATION_INFO rai = _device->GetResourceAllocationInfo(1, 1, _resourceDesc);
-			bx::memSet(ptr, 0, rai.SizeInBytes);
+			bx::memSet(ptr, 0, size_t(rai.SizeInBytes) );
 			resource->Unmap(0, NULL);
 		}