Openvpn – iOS OpenVPN Connect link-mtu differs by 1 byte

I'm seeing this warning in the server-side log when using the OpvenVPN Connect app for iOS:

WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1602',
remote='link-mtu 1603'

The client-side log doesn't show the error. When my other clients (all Tunnelblick/macOS) connect, no warning is generated client- or server-side.
All clients have identical configs.

It's always the same MTU-sizes and they differ by one byte, which is weird to me.
Does anyone know how to fix this?

Thank you!

Server config:

server 10.8.0.0 255.255.255.0
port 443
proto udp4
dev tun
topology subnet
keepalive 10 60
persist-key
persist-tun
user nobody
group nobody
sndbuf 0
rcvbuf 0
max-clients 10
compress lz4-v2
cipher AES-256-CBC
auth SHA512
tls-version-min 1.2
tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
management /tmp/ovpn.sock unix

ifconfig-pool-persist vpn-ipp.txt
status vpn-status.txt
log vpn-messages.log
verb 3
mute 20

ca ca.crt
cert serv.crt
key serv.key
dh dh.pem
tls-auth auth.key 0

iOS Client config:

client
remote servname 443
proto udp

dev tun
resolv-retry infinite
nobind
persist-key
persist-tun
sndbuf 0
rcvbuf 0
mute-replay-warnings

remote-cert-tls server
compress lz4-v2
cipher AES-256-CBC
auth SHA512
tls-version-min 1.2
key-direction 1
<ca></ca>
<cert></cert>
<key></key>
<tls-auth></tls-auth>