SuperTabChain works just once

[powerman]

When trying to autocomplete html file (which have &omnifunc defined) with these settings:

let g:SuperTabDefaultCompletionType = '<c-x><c-u>'
autocmd FileType *
    \ if &omnifunc != '' |
    \   call SuperTabChain(&omnifunc, "<c-p>") |
    \ endif

the omni-complete (in tags) works ok, but when I try to complete usual text outside of html tags I get first <c-p> result when I press <Tab> for the first time, but when I press <Tab> second time nothing happens (looks like it tried to complete text already completed by first <Tab> instead of initial text).

Is this expected behaviour (chaining support only first <c-p> result if &omnifunc fails), or misconfiguration or bug?