diff --git a/include/d3d12.idl b/include/d3d12.idl
index 8430f610..c23d8420 100644
--- a/include/d3d12.idl
+++ b/include/d3d12.idl
@@ -49,6 +49,7 @@ const UINT D3D12_SHADER_COMPONENT_MAPPING_ALWAYS_SET_BIT_AVOIDING_ZEROMEM_MISTAK
         = 1 << (D3D12_SHADER_COMPONENT_MAPPING_SHIFT * 4);
 const UINT D3D12_SIMULTANEOUS_RENDER_TARGET_COUNT = 8;
 const UINT D3D12_CONSTANT_BUFFER_DATA_PLACEMENT_ALIGNMENT = 256;
+const UINT D3D12_DEFAULT_RESOURCE_PLACEMENT_ALIGNMENT = 65536;
 const UINT D3D12_TEXTURE_DATA_PITCH_ALIGNMENT = 256;
 const UINT D3D12_TEXTURE_DATA_PLACEMENT_ALIGNMENT = 512;
 const UINT D3D12_VS_INPUT_REGISTER_COUNT = 32;