diff --git a/principia_make.sh b/principia_make.sh
index 7d627128a..e63edded7 100644
--- a/principia_make.sh
+++ b/principia_make.sh
@@ -4,6 +4,7 @@ cmake \
     -DCMAKE_CXX_COMPILER:FILEPATH="$(which clang++)" \
     -DCMAKE_C_FLAGS="${C_FLAGS?}" \
     -DCMAKE_CXX_FLAGS="${CXX_FLAGS?}" \
+    -DCMAKE_OSX_ARCHITECTURES="x86_64" \
     -DCMAKE_OSX_DEPLOYMENT_TARGET="${OSX_DEPLOYMENT_TARGET}" \
     -DWITH_GFLAGS=OFF \
     -DBUILD_SHARED_LIBS=OFF \