diff --git a/nixos/modules/services/databases/postgresql.nix b/nixos/modules/services/databases/postgresql.nix
index d99ad2c9c7c2..1563858887e6 100644
--- a/nixos/modules/services/databases/postgresql.nix
+++ b/nixos/modules/services/databases/postgresql.nix
@@ -211,6 +211,7 @@ in
             # Shut down Postgres using SIGINT ("Fast Shutdown mode").  See
             # http://www.postgresql.org/docs/current/static/server-shutdown.html
             KillSignal = "SIGINT";
+            KillMode = "process"; # FIXME: this may cause processes to be left behind in the cgroup even after the final SIGKILL
 
             # Give Postgres a decent amount of time to clean up after
             # receiving systemd's SIGINT.