diff --git a/scripts/upgrade b/scripts/upgrade
index 7d3f5bb..34a18ba 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -49,7 +49,10 @@ chown $app:$app "$install_dir/live/.env"
 # Fix SMTP configuration
 config_file=$data_dir/config.json
 cat <<< $(jq -r --arg domain "$domain" '.smtp_host = "$domain"' $config_file) > $config_file
-cat <<< $(jq -r '.smtp_security = starttls' $config_file) > $config_file
+cat <<< $(jq -r '.smtp_security = "starttls"' $config_file) > $config_file
+if [ ! -s "$config_file" ]; then
+    ynh_die --message="Something went wrong while setting up the configuration file: it ended up empty."
+fi
 
 #=================================================
 # REAPPLY SYSTEM CONFIGURATIONS