diff --git a/.github/workflows/engine_js_build.yml b/.github/workflows/engine_js_build.yml
new file mode 100644
index 000000000..36d7c9498
--- /dev/null
+++ b/.github/workflows/engine_js_build.yml
@@ -0,0 +1,18 @@
+name: Test JS build
+
+on:
+  pull_request:
+  merge_group:
+  workflow_dispatch:
+  push:
+    branches: [main]
+    
+jobs:
+  engine-js-build:
+    if: ${{ github.event_name == 'workflow_dispatch' || github.event_name == 'merge_group' }}
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
+    - run: nix build .\#hax-engine.passthru.js -L  
diff --git a/CI.md b/CI.md
index e8aa10b72..d78af2135 100644
--- a/CI.md
+++ b/CI.md
@@ -17,7 +17,9 @@
    FStar, we do not run Coq or FStar on the extractions.
  - [`test_installs`](./.github/workflows/test_installs.yml): compiles
    the toolchain on two versions of Ubuntu and two versions of MacOS
-   using `apt` or `homebrew` and the `setup.sh` script.
+   using `apt` or `homebrew` and the `setup.sh` script;
+ - [`engine-js-build`](./.github/workflows/engine_js_build.yml): tests
+   the build the JS version of the engine.
  
 ## Merge queue
 Additional actions are triggered on pull requests in the merge queue. They are