diff --git a/pkgs/tools/system/mcron/default.nix b/pkgs/tools/system/mcron/default.nix
index a90d6afdc61f..5863504c7040 100644
--- a/pkgs/tools/system/mcron/default.nix
+++ b/pkgs/tools/system/mcron/default.nix
@@ -10,6 +10,11 @@ stdenv.mkDerivation rec {
 
   patches = [ ./install-vixie-programs.patch ];
 
+  # don't attempt to chmod +s files in the nix store
+  postPatch = ''
+    substituteInPlace makefile.in --replace "rwxs" "rwx"
+  '';
+
   buildInputs = [ guile which ed ];
 
   doCheck = true;