can't build a gate like I want to.

[Kandarim]

I have the following set-up, as a cycle lock system at the entrance of my underground base:

I would like to build a small gate between the bottom two cornerposts; however, whenever I try to 'build gate', it gives precedence to the longer gates perpendicular to those.
Even when there are already building signs for those placed, I still can't place the smaller gate. Is there any workaround for this, or am I stuck with this silly setup? (having to expend my gate lock another two tiles, for example)
sealing one of the opposite cornerposts did not make a difference, nor did placing a roundpole fence in between the longer gaps.

EDIT: Okay, I solved it - because the solution was non-obvious, I'll leave this thread around.
Solution:

[jorb]

Minehole blocks the gate? A bit hard to tell. A good practice is perhaps to test the design before committing it to brick.

[Granger]

Same problem as viewtopic.php?f=47&t=54407 - if there are multiple gates possible from the cornerpost that is used to trigger the action the server picks one of them (most likely toward the 'older' cornerpost as it comes first in the list of objects as they seem to be traversed by ObjID), no way to force the game to build toward the other cornerpost(s).