SDL strange behaviour for linux

system: gentoo, SDL-1.2.13
I compile tests from SDL archive. Run checkkeys and short press any key:

When mouse cursor out of window:
kernel test # ./checkkeys
Key pressed: 97-a (a) modifiers: (none)
Key released: 97-a modifiers: (none)

When mouse cursor inside of window:
kernel test # ./checkkeys
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)
Key pressed: 97-a (a) modifiers: (none)

When SDL_EnableKeyRepeat is disabled:
kernel test # ./checkkeys
Key pressed: 97-a (a) modifiers: (none)
Just after leaving cursor from window:
Key released: 97-a modifiers: (none)

The effect is absent when test compiled for windows. Effect is absent with
glfw too.
Probably, the effect is specified for my system? Though I not think so.

Thanx and sorry for my poor english.