diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 37819ac6..979c07f1 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -189,6 +189,8 @@ jobs:
             echo "PYTHON=${PYTHON_INSTALL_PATH}\python.exe" >> $GITHUB_ENV
             echo "GAM_ARCHIVE_ARCH=${GAM_ARCHIVE_ARCH}" >> $GITHUB_ENV
             echo "WIX_ARCH=${WIX_ARCH}" >> $GITHUB_ENV
+            # supposed to tell VS nmake to do parallel build
+            echo "CL=/MP" >> $GITHUB_ENV
           fi
           echo "We'll run make with: ${MAKEOPT}"
           echo "JID=${jid}" >> $GITHUB_ENV