diff --git a/.github/workflows/build-macos.yml b/.github/workflows/build-macos.yml
index 15c62caaa4..77c8cd78bb 100644
--- a/.github/workflows/build-macos.yml
+++ b/.github/workflows/build-macos.yml
@@ -25,7 +25,7 @@ jobs:
         target: 'desktop'
 
     - name: Install Dependencies
-      run: brew install ninja doxygen graphviz protobuf hdf5@1.10 pkg-config
+      run: brew install ninja doxygen graphviz protobuf@21 hdf5@1.10 pkg-config
 
     - name: Install Cap’n Proto
       run: |
@@ -86,7 +86,7 @@ jobs:
         -DECAL_THIRDPARTY_BUILD_QWT=ON \
         -DECAL_THIRDPARTY_BUILD_YAML-CPP=ON \
         -DCMAKE_BUILD_TYPE=Release \
-        -DCMAKE_PREFIX_PATH=/usr/local/opt/hdf5@1.10 \
+        -DCMAKE_PREFIX_PATH=/usr/local/opt/hdf5@1.10;/usr/local/opt/protobuf@21 \
         -DCMAKE_CXX_STANDARD=17 \
         -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=ON \
         -DPython_FIND_STRATEGY=LOCATION \