diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 30b6b9b..d5c9c0c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -119,6 +119,16 @@
           echo "DEPSDIR=`pwd`/deps" >> $GITHUB_ENV
     - name: autogen
       run: |
+          SDKDIR=`xcrun --sdk macosx --show-sdk-path`
+          TESTARCHS="arm64 x86_64"
+          USEARCHS=
+          for ARCH in $TESTARCHS; do
+            if echo "int main(int argc, char **argv) { return 0; }" |clang -arch $ARCH -o /dev/null -isysroot $SDKDIR -x c - 2>/dev/null; then
+              USEARCHS="$USEARCHS -arch $ARCH"
+            fi
+          done
+          export CFLAGS="$USEARCHS -isysroot $SDKDIR"
+          echo "Using CFLAGS: $CFLAGS"
           ./autogen.sh PKG_CONFIG_PATH=/usr/local/lib/pkgconfig --enable-debug \
               openssl_CFLAGS="-I${{ env.DEPSDIR }}/libressl-${{ env.LIBRESSL_VER }}/include" \
               openssl_LIBS="-Xlinker ${{ env.LIBSSL }} -Xlinker ${{ env.LIBCRYPTO }}"