diff --git a/nixos/modules/misc/version.nix b/nixos/modules/misc/version.nix
index 8f246a9278b70..7d644757627f5 100644
--- a/nixos/modules/misc/version.nix
+++ b/nixos/modules/misc/version.nix
@@ -52,7 +52,7 @@ in
 
     stateVersion = mkOption {
       type = types.str;
-      default = cfg.release;
+      default = throw "system.stateVersion needs to be set. Use the value of the current release.";
       description = ''
         Every once in a while, a new NixOS release may change
         configuration defaults in a way incompatible with stateful
diff --git a/nixos/release.nix b/nixos/release.nix
index 6b7564a9b9721..4ad34cf2a10cc 100644
--- a/nixos/release.nix
+++ b/nixos/release.nix
@@ -26,14 +26,16 @@ let
       };
     };
   allTests =
-    foldAttrs recursiveUpdate {} (map allTestsForSystem supportedSystems);
+    foldAttrs recursiveUpdate { } (map allTestsForSystem supportedSystems);
 
   pkgs = import ./.. { system = "x86_64-linux"; };
 
 
   versionModule =
-    { system.nixos.versionSuffix = versionSuffix;
+    {
+      system.nixos.versionSuffix = versionSuffix;
       system.nixos.revision = nixpkgs.rev or nixpkgs.shortRev;
+      system.stateVersion = mkForce "21.04";
     };
 
   makeModules = module: rest: [ configuration versionModule module rest ];
@@ -92,9 +94,10 @@ let
   buildFromConfig = module: sel: forAllSystems (system: hydraJob (sel (import ./lib/eval-config.nix {
     inherit system;
     modules = makeModules module
-      ({ ... }:
+      ({ config, ... }:
       { fileSystems."/".device  = mkDefault "/dev/sda1";
         boot.loader.grub.device = mkDefault "/dev/sda";
+        system.stateVersion = mkDefault config.system.version;
       });
   }).config));