diff --git a/.github/workflows/freebsd.yml b/.github/workflows/freebsd.yml
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+#                          __  __            _
+#                       ___\ \/ /_ __   __ _| |_
+#                      / _ \\  /| '_ \ / _` | __|
+#                     |  __//  \| |_) | (_| | |_
+#                      \___/_/\_\ .__/ \__,_|\__|
+#                               |_| XML parser
+#
+# Copyright (c) 2025 Sebastian Pipping <sebastian@pipping.org>
+# Licensed under the MIT license:
+#
+# Permission is  hereby granted,  free of charge,  to any  person obtaining
+# a  copy  of  this  software   and  associated  documentation  files  (the
+# "Software"),  to  deal in  the  Software  without restriction,  including
+# without  limitation the  rights  to use,  copy,  modify, merge,  publish,
+# distribute, sublicense, and/or sell copies of the Software, and to permit
+# persons  to whom  the Software  is  furnished to  do so,  subject to  the
+# following conditions:
+#
+# The above copyright  notice and this permission notice  shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE  SOFTWARE  IS  PROVIDED  "AS  IS",  WITHOUT  WARRANTY  OF  ANY  KIND,
+# EXPRESS  OR IMPLIED,  INCLUDING  BUT  NOT LIMITED  TO  THE WARRANTIES  OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+# NO EVENT SHALL THE AUTHORS OR  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+# DAMAGES OR  OTHER LIABILITY, WHETHER  IN AN  ACTION OF CONTRACT,  TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+# USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+name: Build in a FreeBSD VM
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: '0 2 * * 5'  # Every Friday at 2am
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  freebsd:
+    name: Build in a FreeBSD VM
+    runs-on: ubuntu-24.04
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+
+    - uses: vmactions/freebsd-vm@8873d98fd1413b5977cb2f7348fe329775159892  # v1.1.9
+      with:
+        release: "15.0"
+        usesh: true
+
+        prepare: |
+          set -e -x
+          pkg install -y \
+              autoconf \
+              automake \
+              bash \
+              cmake \
+              libtool
+
+        run: |
+          set -e -x
+
+          compile_flags='-Wall -Wextra -pedantic -O1 -pipe'
+          export CFLAGS="-std=c99 ${compile_flags}"
+          # TODO C++11 compiler #
+          export CXXFLAGS="-std=c++11 ${compile_flags}"
+
+          cc -v
+          c++ -v
+
+          cd expat
+          ./buildconf.sh
+
+          # 1 of 2: GNU Autotools build system
+          mkdir build_autotools
+          cd build_autotools
+            ../configure --without-tests
+            make -j2 CFLAGS="${CFLAGS} -Werror"
+            # TODO C++11 compiler # make check CFLAGS="${CFLAGS} -Werror" CXXFLAGS="${CXXLAGS} -Werror"
+            make install DESTDIR="${PWD}/ROOT/"
+            find ROOT/
+          cd ..
+
+          # 2 of 2: CMake build system
+          mkdir build_cmake
+          cd build_cmake
+            cmake -S .. -B . -DEXPAT_BUILD_TESTS:BOOL=OFF -DEXPAT_WARNINGS_AS_ERRORS:BOOL=ON
+            make -j2 VERBOSE=1
+            # TODO C++11 compiler # make test VERBOSE=1
+            make install DESTDIR="${PWD}/ROOT/"
+            find ROOT/
+          cd ..