From 1f45d12a2edf755290efa845cfe2f291b41b34f2 Mon Sep 17 00:00:00 2001
From: Stefan Frijters <sfrijters@gmail.com>
Date: Thu, 19 Feb 2026 00:03:50 +0100
Subject: [PATCH] tclPackages.mkTclDerivation: fix clobbering of env

---
 pkgs/development/interpreters/tcl/mk-tcl-derivation.nix | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/interpreters/tcl/mk-tcl-derivation.nix b/pkgs/development/interpreters/tcl/mk-tcl-derivation.nix
index 3a61d556837f..55da68361071 100644
--- a/pkgs/development/interpreters/tcl/mk-tcl-derivation.nix
+++ b/pkgs/development/interpreters/tcl/mk-tcl-derivation.nix
@@ -57,7 +57,10 @@ let
         ];
         propagatedBuildInputs = propagatedBuildInputs ++ [ tcl ];
 
-        env.TCLSH = "${getBin tcl}/bin/tclsh";
+        env = {
+          TCLSH = "${getBin tcl}/bin/tclsh";
+        }
+        // (attrs.env or { });
 
         # Run tests after install, at which point we've done all TCLLIBPATH setup
         doCheck = false;