Opinion by

It was stated in testimony in this case that the land was purchased for plaintiffs and was afterwards deeded to them by Cunningham by general warranty deed.

At the time of the sale to Cunningham and at the time of the delivery of his deed under that sale, there were back taxes due on the lands. Plaintiffs having been compelled to pay these taxes, bring this action on the covenants in the deed.

On trial, the court, against the objection of the plaintiffs, permitted testimony tending to show that at the time of the delivery of the deeds, as required by the written contract of sale, defendant refused to deliver the deed unless Cunningham would agree to pay these back taxes. There was no evidence of any other, further or additional agreement at the time of the sale, other than was incorporated in the written contract. Passing by the question that defendant had not the right to evidence of such subsequent agreement, because not stated in his answer, for the answer puts it “at the time the land was contracted and sold to Cunningham,” we think the evidence wholly incompetent whether the foundation for it was in the answer or not. The full agreement made between the parties had been fulfilled by Cunningham, and after his entire compliance with his agreement, and when defendant was legally bound to deliver him the deed, he, under the threat of refusing the deed, obtains an additional promise that the taxes should be paid. This was a mere naked promise. There was no consideration upon which to base it. Defendant saying he would pay a judgment which existed against him was only agreeing to do what he was bound to do without *523reference to Cunningham’s undertaking. These are familiar and fundamental principles. Landman v. Ingram (49 Mo. 212), does not fit this case. The rule is there correctly laid down that additional consistent considerations may be proved by parol, outside the writing. That is, it must be an additional consideration agreed upon at the time of the contract. So in that case, when the land was sold it was agreed that the payment of taxes was a part of the consideration for the land and this was allowed to be proved as additional to what was expressed in the deed. But here there was no agreement or consideration but that mentioned in the writing, and defendant a month afterwards, undertakes to make an additional bargain. If it had been agreed at the time of the sale that Cunningham was also to pay the taxes, but this had been omitted in the contract, the case of Landman v. Ingram would be authority for the admission of such proof.

The evidence admitted and the instructions based on it were manifestly improper.

The judgment is reversed and the cause remanded.