diff --git a/pkgs/development/compilers/dtc/default.nix b/pkgs/development/compilers/dtc/default.nix
index c5d33590daad..245e5bf2f540 100644
--- a/pkgs/development/compilers/dtc/default.nix
+++ b/pkgs/development/compilers/dtc/default.nix
@@ -1,7 +1,9 @@
 { stdenv, lib, fetchgit, flex, bison, pkg-config, which
-, pythonSupport ? false, python, swig
+, pythonSupport ? false, python ? null, swig
 }:
 
+assert pythonSupport -> python != null;
+
 stdenv.mkDerivation rec {
   pname = "dtc";
   version = "1.6.0";