With multiple pages of search results, the previous and next buttons are flipped

I searched on my site for a string that turned up in 2 pages worth of results. On page 1 of the results, the “Previous” button appears beneath the results (but not “Next”), and on page 2, “Next” appears, but not “Previous”. Also, the buttons seem to do the others’ job (e.g. “Previous” actually takes you to page 2 like “Next” should).