diff --git a/.github/workflows/ci_macos12_clang.yaml b/.github/workflows/ci_macos12_clang.yaml
index 739c700a..090107eb 100644
--- a/.github/workflows/ci_macos12_clang.yaml
+++ b/.github/workflows/ci_macos12_clang.yaml
@@ -22,7 +22,7 @@ jobs:
       run: |
         python3 -m pip install --upgrade pip
         pip3 install tox tox-gh-actions
-        HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 brew install openmpi
+        HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 brew install msgpack openmpi
 
     - name: Run all tests on macOS Monterey 12 with Clang
       run: cd ${GITHUB_WORKSPACE} && make test test_examples
diff --git a/.github/workflows/ci_macos13_clang.yaml b/.github/workflows/ci_macos13_clang.yaml
index 1e5acdb8..340d938e 100644
--- a/.github/workflows/ci_macos13_clang.yaml
+++ b/.github/workflows/ci_macos13_clang.yaml
@@ -20,7 +20,7 @@ jobs:
 
     - name: Install dependencies
       run: |
-        HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 brew install openmpi
+        HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 brew install openmpi msgpack-cxx
         HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 brew install pkg-config
         python3 -m pip install --upgrade pip
         pip3 install tox tox-gh-actions