Snake in boots?

[yisk]

I went on a corridor. Boots there laid. When I have stepped into a cell further, behind me appears a yellow snake. O___O

[DeSt]

Snake pit trap?

[reich]

Any message, like 'Suddenly a pit viper appears!'?

[Timpak]

Since it's a yellow snake it's probably a snake trap, but monsters can also step on teleport traps and wind up next to you.

[yisk]

There was only one snake.
And there was no pit, I have specially returned to look.
On that place simply lies leather boots.