A covenant in any mortgage in the words, “That the buildings on the premises shall be kept insured against loss by fire for the benefit of the holder hereof” shall be construed to have the same force and effect as the following words:

“And it is agreed by and between the parties to these presents that the said mortgagor for himself, his heirs, executors, administrators, successors and assigns, shall and will keep the buildings erected and to be erected upon the lands described in said mortgage insured against loss or damage by fire by insurers and in an amount both approved by the mortgagee, his executors, administrators, successors or assigns, and assign and deliver the policy or policies and the certificates thereof to the said mortgagee, his executors, administrators, successors or assigns, and in default thereof it shall be lawful for the said mortgagee, his executors, administrators, successors or assigns, to effect such insurance, and the premium and premiums paid for effecting the same shall be a lien on said mortgaged premises added to the amount of the said bond or obligation and secured by these presents, payable on demand with legal interest thereon from the time of the payment of such premium or premiums.”