Update primary key on server to not expire

[Wolfgang Pappa]

Hello,

I changed the expiration date on my primary key from "2018-09-22" to "never expire".
On my subkeys I extended the expiration date to "2019-09-24".
On my local machine, everything is fine:

$ gpg --list-keys bbea93c8
pub   rsa4096/BBEA93C8 2014-10-17 [SCA]
      Key fingerprint = A8FC 7FEC 9A68 B5E0 EFA2  5E47 4521 F618 BBEA 93C8
uid         [ultimate] Wolfgang Pappa <wolfgang.pappa at posteo.de>
uid         [ultimate] Wolfgang Pappa <wolfgang.pappa at senckenberg.de>
uid         [ultimate] Living <living at posteo.de>
sub   rsa4096/FB903A9F 2014-10-17 [E] [expires: 2019-09-24]
sub   rsa4096/DF662BA7 2017-09-24 [A] [expires: 2019-09-24]
sub   rsa4096/70B94B54 2017-09-24 [S] [expires: 2019-09-24]

Then I uploaded my key to the keyserver:

$ gpg --keyserver 'https://hkps.pool.sks-keyservers.net' --send-keys BBEA93C8

On the keyserver, only the expiration date of my subkeys got updated. My primary key is marked as expired:

$ curl 'https://hkps.pool.sks-keyservers.net/pks/lookup?op=get&fingerprint=on&search=0x4521F618BBEA93C8' | gpg
pub   rsa4096/BBEA93C8 2014-10-17 [SCA] [expired: 2018-09-22]
      Key fingerprint = A8FC 7FEC 9A68 B5E0 EFA2  5E47 4521 F618 BBEA 93C8
uid                   Living <living at posteo.de>
uid                   Wolfgang Pappa <wolfgang.pappa at posteo.de>
uid                   Wolfgang Pappa <wolfgang.pappa at senckenberg.de>
sub   rsa4096/FB903A9F 2014-10-17 [E] [expired: 2019-09-24]
sub   rsa4096/DF662BA7 2017-09-24 [A] [expired: 2019-09-24]
sub   rsa4096/70B94B54 2017-09-24 [S] [expired: 2019-09-24]

My Question: How can I convince the keyserver to set my primary key’s expiration date to "never expire"?

Cheers,

Wolfgang