diff --git a/mod_image_for_test.sh b/mod_image_for_test.sh
index a41c4e42f4..32e19ca4a5 100755
--- a/mod_image_for_test.sh
+++ b/mod_image_for_test.sh
@@ -173,6 +173,7 @@ IMAGE_NAME="$(basename "$FLAGS_image")"
 ROOT_FS_DIR="$IMAGE_DIR/rootfs"
 STATEFUL_DIR="$IMAGE_DIR/stateful_partition"
 SCRIPTS_DIR=$(dirname "$0")
+DEV_USER="chronos"
 
 trap cleanup EXIT
 
@@ -198,6 +199,9 @@ http:\/\/${FACTORY_SERVER}:8080\/update/" \
 else
   emerge_chromeos_test
 
+  # Mark "OOBE completed" flag so that OEM partition is not mounted on startup.
+  sudo touch "${ROOT_FS_DIR}/home/${DEV_USER}/.oobe_completed"
+
   MOD_TEST_ROOT="${GCLIENT_ROOT}/src/scripts/mod_for_test_scripts"
   # Run test setup script to modify the image
   sudo GCLIENT_ROOT="${GCLIENT_ROOT}" ROOT_FS_DIR="${ROOT_FS_DIR}" \