diff --git a/.github/workflows/check_docs_build.yml b/.github/workflows/check_docs_build.yml
new file mode 100644
index 000000000..55635f610
--- /dev/null
+++ b/.github/workflows/check_docs_build.yml
@@ -0,0 +1,40 @@
+name: ci
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  mkdocs:
+    strategy:
+      matrix:
+        python-version: ["3.11"]
+        os: [ubuntu-latest]
+
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Cache multiple paths
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cache/pip
+            $RUNNER_TOOL_CACHE/Python/*
+            ~\AppData\Local\pip\Cache
+          key: ${{ runner.os }}-build-${{ matrix.python-version }}
+      - name: install-reqs
+        run: python -m pip install --upgrade tox virtualenv setuptools pip -r requirements-dev.txt
+      - name: install-docs-reqs
+        run: python -m pip install --upgrade -r docs/requirements-docs.txt
+      - name: local-install
+        run: python -m pip install -e .
+      - name: check-no-errors
+        run: python -m mkdocs build > output.txt 2>&1
+      - name: assert-no-errors
+        run: python utils/check_for_no_build_errors.py
+      - name: strict-docs-build
+        run: mkdocs build --strict
diff --git a/docs/levels.md b/docs/levels.md
index d632baa6d..bfa580f1a 100644
--- a/docs/levels.md
+++ b/docs/levels.md
@@ -28,6 +28,8 @@ level of support. If a library implements the
 a call such as
 
 ```python exec="1" source="above"
+from typing import Any
+
 import narwhals as nw
 from narwhals.schema import Schema
 
diff --git a/tests/frame/join_test.py b/tests/frame/join_test.py
index f8cafbdf5..9ba119916 100644
--- a/tests/frame/join_test.py
+++ b/tests/frame/join_test.py
@@ -154,7 +154,7 @@ def test_left_join_multiple_column(request: Any, constructor: Any) -> None:
     compare_dicts(result, expected)
 
 
-@pytest.mark.filterwarnings("ignore: the defaultcoalesce behavior")
+@pytest.mark.filterwarnings("ignore: the default coalesce behavior")
 def test_left_join_overlapping_column(request: Any, constructor: Any) -> None:
     if "pyarrow_table" in str(constructor):
         request.applymarker(pytest.mark.xfail)
diff --git a/utils/check_for_no_build_errors.py b/utils/check_for_no_build_errors.py
new file mode 100644
index 000000000..995411e9d
--- /dev/null
+++ b/utils/check_for_no_build_errors.py
@@ -0,0 +1,15 @@
+"""
+Check that `output.txt` doesn't contain the string
+"exited with errors". If it does, exit with status 1.
+
+This is just used in CI.
+"""
+
+import sys
+
+with open("output.txt") as fd:
+    content = fd.read()
+
+if "exited with errors" in content:
+    sys.exit(1)
+sys.exit(0)