diff --git a/src/dawn_native/d3d12/DeviceD3D12.cpp b/src/dawn_native/d3d12/DeviceD3D12.cpp
index 16554b80a6..a91ce6cdfd 100644
--- a/src/dawn_native/d3d12/DeviceD3D12.cpp
+++ b/src/dawn_native/d3d12/DeviceD3D12.cpp
@@ -338,7 +338,7 @@ namespace dawn_native { namespace d3d12 {
 
     size_t Device::GetD3D12HeapTypeToIndex(D3D12_HEAP_TYPE heapType) const {
         ASSERT(heapType > 0);
-        ASSERT(heapType <= kNumHeapTypes);
+        ASSERT(static_cast<uint32_t>(heapType) <= kNumHeapTypes);
         return heapType - 1;
     }