diff --git a/lib.nix b/lib.nix
index c4c6fcf..14266cf 100644
--- a/lib.nix
+++ b/lib.nix
@@ -121,8 +121,8 @@ in
             echo "PostgreSQL initdb process completed"
             echo
           fi
-          substituteAllInPlace $PGDATA/postgresql.conf
-          cp ${configFile} $PGDATA/postgresql.conf
+          substituteAllInPlace "$PGDATA"/postgresql.conf
+          cp ${configFile} "$PGDATA"/postgresql.conf
           if [[ "$POSTGRES_RUN_INITIAL_SCRIPT" == "true" ]]; then
             echo
             echo "PostgreSQL is setting up the initial database"