diff --git a/flake.lock b/flake.lock
index deccc28..fcffc3a 100644
--- a/flake.lock
+++ b/flake.lock
@@ -147,6 +147,7 @@
       },
       "original": {
         "owner": "simple-nixos-mailserver",
+        "ref": "nixos-21.11",
         "repo": "nixos-mailserver",
         "type": "gitlab"
       }
diff --git a/flake.nix b/flake.nix
index ea4121d..d48c84f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -10,25 +10,24 @@
 
     # simple mailserver
     snm = {
-      url = "gitlab:simple-nixos-mailserver/nixos-mailserver";
+      url = "gitlab:simple-nixos-mailserver/nixos-mailserver/nixos-21.11";
       inputs.nixpkgs.follows = "nixpkgs";
       inputs.flake-utils.follows = "utils/flake-utils";
     };
 
     # age for nix to store encrypted passwords conveniently
-    agenix ={
+    agenix = {
       url = "github:ryantm/agenix";
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
-  outputs = { self, hm, nixpkgs, agenix, ... }@inputs: {
-    inherit self inputs;
 
+  outputs = { self, hm, nixpkgs, agenix, snm, ... }@inputs: {
     nixosConfigurations."thrall" = nixpkgs.lib.nixosSystem {
       system = "x86_64-linux";
       modules = [
         ({ nixpkgs = { config.allowUnfree = true; }; })
-        inputs.snm.nixosModule
+        snm.nixosModule
         ./modules/security.nix
         ./hosts/thrall
         agenix.nixosModules.age