diff --git a/lib.nix b/lib.nix
index d9c74e7..1c7a2af 100644
--- a/lib.nix
+++ b/lib.nix
@@ -142,7 +142,7 @@ in
         name = "run-postgres";
         text = ''
             set -euo pipefail
-            export PGDATA=${data_dir} PGHOST=${runtimeDir} PGPORT=${builtins.toString port}
+            export PGDATA=$(pwd)/${data_dir} PGHOST=$(pwd)/${runtimeDir} PGPORT=${builtins.toString port}
           pwd
             mkdir -p ${lib.escapeShellArg runtimeDir}
             ${setupScript}/bin/setup-postgres