Accessing the Clang stdlib in a Nix shell

I have a Nix shell (in nix-cargo-integration) that pulls in Clang and sets an environment variable for extra Clang arguments. I need this in order to build a huge library. However, upon invoking clang, I get the following error:

fatal error: 'initializer_list' file not found

Where can I find initializer_list - and for that matter, its accompanying standard library - in Nix?