diff --git a/src/PVE/Network.pm b/src/PVE/Network.pm
index 366d242..2d63a45 100644
--- a/src/PVE/Network.pm
+++ b/src/PVE/Network.pm
@@ -594,6 +594,8 @@ sub is_ip_in_cidr {
 
     my $overlap = $cidr_obj->overlaps($ip_obj);
 
+    return if !defined($overlap);
+
     return $overlap == $Net::IP::IP_B_IN_A_OVERLAP || $overlap == $Net::IP::IP_IDENTICAL;
 }