There were grammatical errors even in his silence.

[Nawet w jego milczeniu były błędy językowe.]

Stanislaw Lec (1909-1966) Polish aphorist, poet, satirist

Unkempt Thoughts [Myśli nieuczesane] (1957) [tr. Gałązka (1962)]
    (Source)

Alternate translation: "Even in his silence were grammatical errors."