"[CISG] Article 40 was taken almost word-for-word from Article 40 ULIS and gave no cause for discussion during the drawing up of the Convention." Schwenzer, in: Peter Schlechtriem ed., Commentary on the UN Convention on the International Sale of Goods, Oxford (1998) 321 [citations omitted]
CISG Article 40 ULIS Article 40
The seller shall not be entitled The seller shall not be entitled
to rely on the provisions of to rely on the provisions of
articles 38 and 39 if the lack of Articles 38 and 39 if the lack
of conformity relates to facts of conformity relates to facts
of which he knew or could not of which he knew, or of which
have been unaware and which he could not have been unaware,
he did not disclose to the buyer. and which he did not disclose.