The talk explores past stem alternations in Ishkashimi. First, I examine the regular verbs. They have two different past allomorphs (d and ǝd), and I claim that this distinction cannot be fully explained by phonology; therefore, ǝ can be treated as a theme vowel. Next, there is a class of verbs showing weak suppletion. The patterns of vowel and consonant changes are not automatic, so they are also treated as part of the morphology component of the grammar.