Tmux stops responding to key bindings after xclip usage

I use Tmux version 1.9. To push tmux's clipboard to my X clipboard I have such a string in tmux.conf:

bind C-c run "tmux save-buffer - | xclip -i -sel clipboard"

The problem is that after pressing C-b C-c content of tmux's buffer goes to the X clipboard, but also all the key bindings stop working.

I can't create a new window, pane, etc.

Has anyone faced such a problem?

UPD

After a about a minute tmux starts responding to C-b bindings.