diff --git a/gnome-session/leader-main.c b/gnome-session/leader-main.c
index 511166d6..8bac2912 100644
--- a/gnome-session/leader-main.c
+++ b/gnome-session/leader-main.c
@@ -92,6 +92,9 @@ maybe_reexec_with_login_shell (GStrv argv)
 
         g_debug ("Relaunching with login shell %s (%s)", login_shell, shell);
 
+        /* Make sure the shell actually sets up the environment */
+        g_unsetenv ("__NIXOS_SET_ENVIRONMENT_DONE");
+
         /* First, we construct the command executed by the login shell */
         builder = g_strv_builder_new ();
         g_strv_builder_add (builder, "exec");