A grantor who has conveyed by an effective, unambiguous instrument cannot, by executing another instrument, make a substantial change in the name of the grantee, decrease the size of the premises or the extent of the estate granted, impose a condition or limitation upon the interest granted, or otherwise derogate from the first grant, even though the latter instrument purports to correct or modify the former. However, marketability dependent upon the effect of the first instrument is not impaired by the second instrument.
SDCL app TO CHAPTER 43-30 § 7-11