diff --git a/src/ctypesgen/__main__.py b/src/ctypesgen/__main__.py
index 23ee014..2d0cfc1 100644
--- a/src/ctypesgen/__main__.py
+++ b/src/ctypesgen/__main__.py
@@ -89,17 +89,9 @@ def main_impl(args, cmd_str):
         assert _is_relative_to(args.output, args.linkage_anchor)
     
     if args.cpp:
-        assert shutil.which(args.cpp[0]), f"Given pre-processor {args.cpp[0]!r} is not available."
-    else:
-        if shutil.which("gcc"):
-            args.cpp = ["gcc", "-E"]
-        elif shutil.which("cpp"):
-            args.cpp = ["cpp"]
-        elif shutil.which("clang"):
-            args.cpp = ["clang", "-E"]
-        else:
-            raise RuntimeError("C pre-processor auto-detection failed: neither gcc nor clang available.")
-    
+        print("cpp argument ignored for nix build")
+    args.cpp = ["@cc@", "-E"]
+ 
     # Important: must not use +=, this would mutate the original object, which is problematic when default=[] is used and ctypesgen called repeatedly from within python
     args.compile_libdirs = args.compile_libdirs + args.universal_libdirs
     args.runtime_libdirs = args.runtime_libdirs + args.universal_libdirs