Sleepy Duskywings occur throughout much of the United States (see map) but are extremely rare (S1) in Ontario, present in small numbers in only three locations. This one was found in dry oak woods just south of Pinery Provincial Park. Habitat is a good way to separate this species (Erynnis brizo) from the similar-looking Dreamy Duskywing (Erynnis icelus), which occurs in moist willow/poplar habitat. These two species are the only Canadian duskywings that lack white forewing spots.
Compare to Daniel's image of a Dreamy Duskywing in the Guide. His ID must be correct because the Sleepy Duskywing doesn't occur in Quebec.