diff --git a/nixos/modules/burrow-zulip.nix b/nixos/modules/burrow-zulip.nix
index b5e72b7..3417925 100644
--- a/nixos/modules/burrow-zulip.nix
+++ b/nixos/modules/burrow-zulip.nix
@@ -179,6 +179,7 @@ in
         pkgs.bash
         pkgs.coreutils
         pkgs.python3
+        pkgs.shadow
       ];
       serviceConfig = {
         Type = "oneshot";
@@ -204,7 +205,7 @@ END
 ALTER ROLE zulip WITH LOGIN PASSWORD '$db_password_sql';
 SQL
 
-        su postgres -s ${pkgs.bash}/bin/bash -c "psql -v ON_ERROR_STOP=1 -f '$setup_sql'"
+        ${pkgs.shadow}/bin/su postgres -s ${pkgs.bash}/bin/bash -c "psql -v ON_ERROR_STOP=1 -f '$setup_sql'"
       '';
     };