diff --git a/scripts/build-mainline-modules.sh b/scripts/build-mainline-modules.sh
index ea62af4a2..b8485ea3d 100755
--- a/scripts/build-mainline-modules.sh
+++ b/scripts/build-mainline-modules.sh
@@ -61,6 +61,9 @@ lib_dir() {
   esac
 }
 
+# Make sure this build builds from source, regardless of the default.
+export SOONG_CONFIG_art_module_source_build=true
+
 OUT_DIR=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT= get_build_var OUT_DIR)
 DIST_DIR=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT= get_build_var DIST_DIR)