diff --git a/src/scripts/setblocklist.sh b/src/scripts/setblocklist.sh
index 70fbed67d..b0ddc5698 100755
--- a/src/scripts/setblocklist.sh
+++ b/src/scripts/setblocklist.sh
@@ -21,6 +21,6 @@ if [[ -f "${user_firewall_json}" ]]; then
     while read -r line || [[ -n "$line" ]]; do
         [[ -z "${line}" ]] && continue # ignore empty lines
         [[ "$line" =~ ^#.*$ ]] && continue # ignore lines starting with #
-        ipset add cloudron_blocklist "${line}"
+        ipset add -! cloudron_blocklist "${line}" # the -! ignore duplicates
     done < "${user_firewall_json}"
 fi