diff --git a/Cronet/tools/import/import_cronet.sh b/Cronet/tools/import/import_cronet.sh
index 6639a4c..0f04af7 100755
--- a/Cronet/tools/import/import_cronet.sh
+++ b/Cronet/tools/import/import_cronet.sh
@@ -24,6 +24,8 @@
 #   -n rev: The new revision to import.
 #   -f: Force copybara to ignore a failure to find the last imported revision.
 
+set -e -x
+
 OPTSTRING=fl:n:
 
 usage() {
@@ -55,7 +57,7 @@
 # Arguments:
 #   new_rev, string
 #######################################
-setup_folder_origin() {
+setup_folder_origin() (
     local _new_rev=$1
     mkdir -p "${COPYBARA_FOLDER_ORIGIN}"
     cd "${COPYBARA_FOLDER_ORIGIN}"
@@ -83,9 +85,10 @@
     cd src
     # Set appropriate gclient flags to speed up syncing.
     gclient sync \
-        --no-history
-        --shallow
-}
+        --no-history \
+        --shallow \
+        --delete_unversioned_trees
+)
 
 #######################################
 # Runs the copybara import of Chromium