diff --git a/include/d3d12.idl b/include/d3d12.idl
index 991be73d..4b6f68c3 100644
--- a/include/d3d12.idl
+++ b/include/d3d12.idl
@@ -256,6 +256,7 @@ typedef enum D3D12_RESOURCE_STATES
     D3D12_RESOURCE_STATE_PRESENT = 0x0,
     D3D12_RESOURCE_STATE_PREDICATION = 0x200,
 } D3D12_RESOURCE_STATES;
+cpp_quote("DEFINE_ENUM_FLAG_OPERATORS(D3D12_RESOURCE_STATES);")
 
 typedef enum D3D12_RESOURCE_BARRIER_TYPE
 {