diff --git a/nix/mk_tests.nix b/nix/mk_tests.nix
index 413a24321b4c2a7fd55e5b9310e1dcd75d4d20a8..302f6140ce1c7cd4f6786e7d706441ee907aae6d 100644
--- a/nix/mk_tests.nix
+++ b/nix/mk_tests.nix
@@ -2,9 +2,9 @@
 , alt-ergo
 , frama-c
 , perl
-, pkgs
 , stdenvNoCC
 , time
+, unixtools
 , which
 } :
 
@@ -24,8 +24,8 @@ stdenvNoCC.mkDerivation {
   buildInputs = frama-c.buildInputs ++ [
     frama-c
     perl
-    pkgs.getopt
     time
+    unixtools.getopt
     which
   ] ++
   (if has-wp-proofs then [ alt-ergo ] else []);