diff --git a/modules/dev-services.nix b/modules/dev-services.nix
index d7c9c9b..caa2370 100644
--- a/modules/dev-services.nix
+++ b/modules/dev-services.nix
@@ -1,5 +1,5 @@
 # Development services module - Matrix, Forgejo, and Slack bridge
-{ config, pkgs-unstable, lib, ... }:
+{ config, pkgs, pkgs-unstable, lib, ... }:
 
 with lib;
 
@@ -99,8 +99,10 @@ in
 
   config = mkIf cfg.enable {
     # PostgreSQL for Forgejo and bridge services (Matrix uses RocksDB)
+    # Pin to v15 to prevent auto-upgrade to v16 in NixOS 24.11
     services.postgresql = {
       enable = true;
+      package = pkgs.postgresql_15;
       ensureDatabases = [
         "forgejo"
       ] ++ optional cfg.slackBridge.enable "mautrix_slack";