diff --git a/pkg/util/ipset/ipset.go b/pkg/util/ipset/ipset.go
index 56993c26305..7ae28050097 100644
--- a/pkg/util/ipset/ipset.go
+++ b/pkg/util/ipset/ipset.go
@@ -329,10 +329,13 @@ func IsNotFoundError(err error) bool {
 	es := err.Error()
 	if strings.Contains(es, "does not exist") {
 		// set with the same name already exists
+		// xref: https://github.com/Olipro/ipset/blob/master/lib/errcode.c#L32-L33
 		return true
 	}
 	if strings.Contains(es, "element is missing") {
 		// entry is missing from the set
+		// xref: https://github.com/Olipro/ipset/blob/master/lib/parse.c#L1904
+		// https://github.com/Olipro/ipset/blob/master/lib/parse.c#L1925
 		return true
 	}
 	return false