diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
new file mode 100644
index 0000000..0c7ef65
--- /dev/null
+++ b/.github/workflows/check.yml
@@ -0,0 +1,23 @@
+name: Check
+
+on:
+  workflow_dispatch:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - uses: cachix/install-nix-action@v23
+      with:
+        extra_nix_config: |
+          accept-flake-config = true
+
+    - name: Smoke-test the library function
+      run: nix develop -c just check-function
diff --git a/flake.nix b/flake.nix
index e06b289..dc218f6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,6 +13,7 @@
   outputs = {
     systems,
     nixpkgs,
+    self,
     ...
   } @ inputs: let
     inherit (nixpkgs) lib;
@@ -33,6 +34,18 @@
   in {
     data = import ./generated;
 
+    lib.builtinLibrariesOfEmacsVersion = targetVersion: let
+      xs =
+        builtins.map ({libraries, ...}: libraries)
+        (
+          builtins.filter ({version, ...}: version == targetVersion)
+          (builtins.attrValues self.data)
+        );
+    in
+      if builtins.length xs > 0
+      then builtins.head xs
+      else null;
+
     devShells = eachSystem (pkgs: {
       default = pkgs.mkShell {buildInputs = [pkgs.just];};
     });
diff --git a/justfile b/justfile
index 0b9142e..fd7c066 100644
--- a/justfile
+++ b/justfile
@@ -4,3 +4,6 @@ update:
     mkdir -p generated
     rm -f generated/*.nix
     install -m 644 $(nix build . --print-out-paths)/*.nix generated/
+
+check-function:
+    nix eval .\#lib.builtinLibrariesOfEmacsVersion --apply 'f: f "29.1"'