diff --git a/config/upgrade.sh b/config/upgrade.sh
old mode 100755
new mode 100644
index 67a5008..564b3e3
--- a/config/upgrade.sh
+++ b/config/upgrade.sh
@@ -14,7 +14,7 @@ cd /opt/scodoc/Products/ScoDoc/config
 source config.sh
 source utils.sh
 
-check_uid_root $0
+check_uid_root "$0"
 
 if [ -z "$SCODOC_UPGRADE_RUNNING" ]
    then
@@ -23,7 +23,8 @@ fi
 
 # Upgrade svn working copy if possible
 svnver=$(svn --version --quiet)
-if [[ ${svnver} > "1.7" ]]
+# shellcheck disable=SC2072
+if [[ ${svnver} > "1.7" ]] 
 then
  (cd "$SCODOC_DIR"; find . -name .svn -type d -exec dirname {} \; | xargs svn upgrade)
 fi
@@ -63,7 +64,7 @@ CMD="curl --fail --connect-timeout 5 --silent http://scodoc.iutv.univ-paris13.fr
 #echo $CMD
 SVERSION="$(${CMD})"
 
-if [ $? == 0 ]; then
+if [ "$?" == 0 ]; then
   #echo "answer=${SVERSION}" 
   echo "${SVERSION}" > "${SCODOC_VERSION_DIR}"/scodoc.sn
 else
@@ -72,13 +73,13 @@ fi
 
 
 # Check that no Zope "access" file has been forgotten in the way:
-if [ -e $SCODOC_DIR/../../access ]
+if [ -e "$SCODOC_DIR"/../../access ]
 then
-  mv $SCODOC_DIR/../../access $SCODOC_DIR/../../access.bak
+  mv "$SCODOC_DIR"/../../access "$SCODOC_DIR"/../../access.bak
 fi
 
 # Fix some permissions which may have been altered in the way:
-chsh -s /bin/sh $POSTGRES_USER # www-data, nologin in Debian 9
+chsh -s /bin/sh "$POSTGRES_USER" # www-data, nologin in Debian 9
 chown root.www-data "$SCODOC_DIR" # important to create .pyc
 chmod 775 "${SCODOC_DIR}"
 chmod a+r "$SCODOC_DIR"/*.py
@@ -119,7 +120,9 @@ then
        /opt/zope213/bin/pip install requests
 fi
 
-/opt/zope213/bin/pip install --upgrade python-dateutil
+# upgrade old dateutil (check version manually to speedup)
+v=$(/opt/zope213/bin/python -c "import dateutil; print dateutil.__version__")
+[[ "$v" < "2.8.1" ]] && /opt/zope213/bin/pip install --upgrade python-dateutil
 
 # Ensure www-data can duplicate databases (for dumps)
 su -c $'psql -c \'alter role "www-data" with CREATEDB;\'' "$POSTGRES_SUPERUSER"
@@ -130,7 +133,7 @@ echo "Executing post-upgrade script..."
 "$SCODOC_DIR"/config/postupgrade.py
 
 echo "Executing post-upgrade database script..."
-su -c "$SCODOC_DIR/config/postupgrade-db.py" $POSTGRES_USER
+su -c "$SCODOC_DIR/config/postupgrade-db.py" "$POSTGRES_USER"
 
 # 
 echo