In T 1644/10, the EPO had published an incorrect patent specification B1 and subsequently corrected it as B9. The appellant had relied on the accuracy of the published specification B1 and consequently failed to file notice of opposition within the prescribed period. The board held that whether the protection of legitimate expectations could be applied in an inter partes procedure where there had been a failure to meet the opposition deadline was subject to a weighing-up of interests. There was no general rule that the patentee's legitimate expectation that the grant decision had become final had to be considered subordinate to the opponent's legitimate expectation that the content of the published patent specification was correct. That would run counter to the rule of equal procedural treatment of the parties. In the case at hand, the appellant could not rely on the applicability of the principle of legitimate expectations in relation to its failure to meet the opposition deadline.