The right to avoid a contract for the sale of realty,1 as for the vendor's failure to furnish an abstract of title,2 or because of a defect in the title,3 or because a building on the property extends over the boundary line,4 may be waived, even after a notice of forfeiture has been given, if both parties treat the contract as still in force.5 A contract for the sale of land, requiring the vendee to pay taxes, is not discharged by vendee's failure to pay such taxes where subsequently the vendor recognizes such contract as in full force.6