diff --git a/lib.nix b/lib.nix
index adf79ac..be30b2a 100644
--- a/lib.nix
+++ b/lib.nix
@@ -142,9 +142,10 @@ in
         name = "run-postgres";
         text = ''
           set -euo pipefail
-          export PGDATA=${data_dir}
-          export PGHOST=${runtimeDir}
-          export PGPORT=${builtins.toString port}
+          PGDATA=${data_dir}
+          PGHOST=${runtimeDir}
+          PGPORT=${builtins.toString port}
+          export PGDATA PGHOST PGPORT
           mkdir -p ${lib.escapeShellArg runtimeDir}
           ${setupScript}/bin/setup-postgres
           ${package}/bin/postgres