John T. Zimmer described Xiphorhynchus necopinus (Zimmer's Woodcreeper) as a sibling species of the more widespread Xiphorhynchus picus (Straight-billed Woodcreeper). Despite his initial suspicion that a preexisting name (kienerii) could be applied to the new species he described, Zimmer discarded that possibility without directly examining the type of X. p. kienerii housed at the Museum National D'Histoire Naturelle in Paris, France. We studied plumage and measured wing chord and tail lengths of the type specimen of X. p. kienerii, comparing it with series of specimens of X. necopinus and X. picus. We show that X. necopinus and the type of X. p. kienerii are morphologically and morphometrically indistinguishable, and thus necopinus is synonymized with kienerii, the name that has priority. Because Zimmer mistakenly applied the name kienerii to a western Amazonian population of X. picus, most specimens in museums identified as X. p. kienerii after Zimmer's review (Zimmer 1934) are likely to refer to X. p. peruvianus.