diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2e751c5f..6e9e5485 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -5,6 +5,35 @@ on:
   pull_request:
 
 jobs:
+  build-openbsd:
+    runs-on: ubuntu-latest
+    name: build • openbsd
+    defaults:
+      run:
+        shell: openbsd {0}
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Start OpenBSD VM
+        uses: vmactions/openbsd-vm@v1
+        with:
+          prepare: |
+            pkg_add -v cmake ninja git python bash
+          run: |
+            git clone --depth=1 https://codeberg.org/OpenBSD/ports.git /usr/ports
+          sync: 'rsync'
+          copyback: false
+
+      - name: Install capnproto
+        run: |
+          cd /usr/ports/devel/capnproto/
+          make install
+
+      - name: Run CI script
+        run: |
+          cd ${{ github.workspace }}
+          CI_CONFIG="ci/configs/openbsd.bash" bash ci/scripts/ci.sh
+
   build:
     runs-on: ubuntu-latest
 
@@ -16,7 +45,7 @@ jobs:
     name: build • ${{ matrix.config }}
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install Nix
         uses: cachix/install-nix-action@v31       # 2025-05-27, from https://github.com/cachix/install-nix-action/tags
diff --git a/ci/configs/openbsd.bash b/ci/configs/openbsd.bash
new file mode 100644
index 00000000..a404e2bc
--- /dev/null
+++ b/ci/configs/openbsd.bash
@@ -0,0 +1,5 @@
+CI_DESC="CI config for OpenBSD"
+CI_DIR=build-openbsd
+export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter"
+CMAKE_ARGS=(-G Ninja)
+BUILD_ARGS=(-k 0)
diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index 0e758d57..7da049c3 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -24,6 +24,5 @@ add_executable(mpexample
 target_capnp_sources(mpexample ${CMAKE_CURRENT_SOURCE_DIR} init.capnp calculator.capnp printer.capnp)
 target_include_directories(mpexample PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 target_link_libraries(mpexample PRIVATE Threads::Threads)
-target_link_libraries(mpexample PRIVATE stdc++fs)
 
 add_custom_target(mpexamples DEPENDS mpexample mpcalculator mpprinter)
diff --git a/src/mp/util.cpp b/src/mp/util.cpp
index a9485399..da7c3b0b 100644
--- a/src/mp/util.cpp
+++ b/src/mp/util.cpp
@@ -16,6 +16,7 @@
 #include <sys/socket.h>
 #include <sys/wait.h>
 #include <system_error>
+#include <thread> // NOLINT(misc-include-cleaner) // IWYU pragma: keep
 #include <unistd.h>
 #include <utility>
 #include <vector>