Where the only testimony as to whether or not there was a modification of the agreement of defendant that plaintiff, a real estate agent, should have a commission if a trade of defendant's property was made with S., was defendant's testimony, contradicted by plaintiff, that after the first attempt at a trade had failed, he had a conversation with plaintiff, in which plaintiff said that S. would not trade, and that they would drop the deal, and that if defendant disposed of the property himself, or through another agent, he did not expect a commission; that he only expected one if he closed the deal himself; the only question for the jury was whether such conversation occurred, as, if it did, plaintiff would be presumed to have understood it, so that, the sale having been consummated by another agent, it was error to instruct that for defendant to escape liability to plaintiff he must show, not only that he understood plaintiff had waived his claim to a com-' mission, but also that plaintiff understood that he was to waive such claim. Romans v. Thew (Iowa Sup. '09), 120 N. W. 629.