diff --git a/website/content/en/releases/13.0R/errata.adoc b/website/content/en/releases/13.0R/errata.adoc
--- a/website/content/en/releases/13.0R/errata.adoc
+++ b/website/content/en/releases/13.0R/errata.adoc
@@ -67,3 +67,8 @@
 [2021-04-05] A very late issue was discovered in the [.filename]#/usr/bin/dc# program.
 The "P" command does not correctly pop the top of stack value and this will break complex scripts that continue after printing a result.
 The [.filename]#/usr/bin/bc# program is not affected, since it does not depend on dc as its execution engine.
+
+[2021-04-14] An issue was discovered where during an upgrade, when the kernel is new but [.filename]#/sbin/ifconfig# is still the previous version, VLAN interfaces are configured with an invalid ethernet protocol type.
+This causes the VLAN interfaces to send invalid traffic, resulting in non-functional networking.
+Once the updated [.filename]#/sbin/ifconfig# binary is installed, VLANs are created correctly.
+When depending on network access via VLANs during the upgrade, it is suggested to install the new world (run the second `freebsd-upgrade install`) before rebooting.