diff --git a/flake.lock b/flake.lock
index 12aa181..3b15c48 100644
--- a/flake.lock
+++ b/flake.lock
@@ -49,11 +49,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1718530797,
-        "narHash": "sha256-pup6cYwtgvzDpvpSCFh1TEUjw2zkNpk8iolbKnyFmmU=",
+        "lastModified": 1722185531,
+        "narHash": "sha256-veKR07psFoJjINLC8RK4DiLniGGMgF3QMlS4tb74S6k=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b60ebf54c15553b393d144357375ea956f89e9a9",
+        "rev": "52ec9ac3b12395ad677e8b62106f0b98c1f8569d",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 6a83ec1..b7b412a 100644
--- a/flake.nix
+++ b/flake.nix
@@ -36,11 +36,12 @@
 
         packages.system-profile = import ./system-profile.nix { inherit pkgs flakey-profile; };
 
-        nixosTests = pkgs.recurseIntoAttrs (pkgs.callPackage ./test-nixos.nix { lix-module = self.nixosModules.default; });
+        nixosTests = pkgs.recurseIntoAttrs (pkgs.callPackage ./test-nixos.nix { inherit pkgs; lix-module = self.nixosModules.default; });
 
         checks = {
           inherit (self.packages.${system}) default nix-eval-jobs;
         } // lib.optionalAttrs (lib.elem system linux64BitSystems) {
+          # wrongMajor intentionally not included here since it is expected to fail
           inherit (self.nixosTests.${system}) it-builds;
         };
       });
diff --git a/overlay.nix b/overlay.nix
index cc1a04b..caa3a65 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -5,7 +5,7 @@ let
   # 2.18 since nixpkgs can introduce new breakage in its Nix unstable CLI
   # usage.
   # https://github.com/nixos/nixpkgs/blob/6afb255d976f85f3359e4929abd6f5149c323a02/nixos/modules/config/nix.nix#L121
-  lixPkgFromSource = final.callPackage (lix + "/package.nix") ({
+  lixPackageFromSource = final.callPackage (lix + "/package.nix") ({
     versionSuffix = "-${versionSuffix}";
     # FIXME: do this more sensibly for future releases
     # https://git.lix.systems/lix-project/lix/issues/406
@@ -28,8 +28,13 @@ let
       nix = final.nixVersions.nix_2_18_upstream;
     });
 
+  inherit (prev) lib;
+
+  csi = builtins.fromJSON ''"\u001b"'';
+  orange = "${csi}[35;1m";
+  normal = "${csi}[0m";
   warning = ''
-    warning: You have the lix overlay included into a nixpkgs import twice,
+    ${orange}warning${normal}: You have the lix overlay included into a nixpkgs import twice,
     perhaps due to the NixOS module being included twice, or because of using
     pkgs.nixos and also including it in imports, or perhaps some unknown
     machinations of a complicated flake library.
@@ -42,9 +47,25 @@ let
     delete that.
     P.P.S. This Lix has super catgirl powers.
   '';
+  wrongMajorWarning = ''
+    ${orange}warning${normal}: This Lix NixOS module is being built against a Lix with a
+    major version (got ${lixPackageToUse.version}) other than the one the
+    module was designed for (expecting ${supportedLixMajor}). Some downstream
+    packages like nix-eval-jobs may be broken by this. Consider using a
+    matching version of the Lix NixOS module to the version of Lix you are
+    using.
+  '';
 
   maybeWarnDuplicate = x: if final.lix-overlay-present > 1 then builtins.trace warning x else x;
 
+  versionJson = builtins.fromJSON (builtins.readFile ./version.json);
+  supportedLixMajor = builtins.elemAt (builtins.match ''^([[:digit:]]+\.[[:digit:]]+)\..*'' versionJson.version) 0;
+  lixPackageToUse = if lix != null then lixPackageFromSource else prev.lix;
+  # Especially if using Lix from nixpkgs, it is plausible that the overlay
+  # could be used against the wrong Lix major version and cause confusing build
+  # errors. This is a simple safeguard to put in at least something that might be seen.
+  maybeWarnWrongMajor = x: if !(lib.hasPrefix supportedLixMajor lixPackageToUse.version) then builtins.trace wrongMajorWarning x else x;
+
   overlay = override_2_18 // {
     lix-overlay-present = 1;
     # used for things that one wouldn't necessarily want to update, but we
@@ -52,11 +73,10 @@ let
     # want to do that.
     lix-sources = import ./pins.nix;
 
-    lix = if lix != null then lixPkgFromSource else prev.lix;
+    lix = maybeWarnWrongMajor (maybeWarnDuplicate lixPackageToUse);
 
     nixVersions = prev.nixVersions // rec {
-      # FIXME: do something less scuffed
-      nix_2_18 = maybeWarnDuplicate final.lix;
+      nix_2_18 = final.lix;
       stable = nix_2_18;
       nix_2_18_upstream = prev.nixVersions.nix_2_18;
     };
diff --git a/test-nixos.nix b/test-nixos.nix
index 376eaf0..b6fef10 100644
--- a/test-nixos.nix
+++ b/test-nixos.nix
@@ -1,5 +1,8 @@
-{ nixos, lix-module }:
+{ pkgs, nixos, lix-module }:
 let
+  pkgs' = import pkgs.path {
+    inherit (pkgs) system;
+  };
   configs = {
     it-builds = nixos ({ ... }: {
       imports = [ lix-module ];
@@ -9,10 +12,21 @@ let
       system.stateVersion = "24.05";
     });
 
+    # Intentionally provoke the wrong major version.
+    # Does assume that the module is one major ahead of the release; the main
+    # purpose here is a manual testing fixture.
+    wrongMajor = pkgs'.nixos ({ ... }: {
+      imports = [ (import ./module.nix { lix = null; }) ];
+      documentation.enable = false;
+      fileSystems."/".device = "ignore-root-device";
+      boot.loader.grub.enable = false;
+      system.stateVersion = "24.05";
+    });
   };
 in
 {
   inherit configs;
 
   it-builds = configs.it-builds.config.system.build.toplevel;
+  wrongMajor = configs.wrongMajor.config.system.build.toplevel;
 }
diff --git a/version.json b/version.json
new file mode 100644
index 0000000..808e1b1
--- /dev/null
+++ b/version.json
@@ -0,0 +1,3 @@
+{
+    "version": "2.91.0-dev"
+}