diff --git a/builtin/last-modified.c b/builtin/last-modified.c
index b0ecbdc5400d137b7e147c8f91f43210cf8236e0..cc5fd2e7950be746443faae831c36aa9fd09e0d5 100644
--- a/builtin/last-modified.c
+++ b/builtin/last-modified.c
@@ -327,7 +327,7 @@ static void process_parent(struct last_modified *lm,
 	if (!(parent->object.flags & PARENT1))
 		active_paths_free(lm, parent);
 
-	memset(lm->scratch->words, 0x0, lm->scratch->word_alloc);
+	memset(lm->scratch->words, 0x0, lm->scratch->word_alloc * sizeof(eword_t));
 	diff_queue_clear(&diff_queued_diff);
 }