"Under Siege" icon missing

[Leyrann]

The city should be under siege, and it is (it did not heal last turn), but the icon is missing.

 

[Jaybe]

I was never sure that ranged units exerted a ZOC on the hex they occupy. Obviously that had an effect on the siege notification but at least it didn't on the siege itself.

 

[Leyrann]

I was never sure that ranged units exerted a ZOC on the hex they occupy. Obviously that had an effect on the siege notification but at least it didn't on the siege itself.

I've used them in this way before, and indeed they have ZOC on their own tile, but normally the icon always appears.