diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/MigrateUseCase.kt b/app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/MigrateUseCase.kt
index 4a061af87..b771bd9a3 100644
--- a/app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/MigrateUseCase.kt
+++ b/app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/MigrateUseCase.kt
@@ -91,7 +91,7 @@ class MigrateUseCase @Inject constructor(
 		val oldChapters = checkNotNull(oldManga.getChapters(branch))
 		var index = oldChapters.indexOfFirst { it.id == history.chapterId }
 		if (index < 0) {
-			index = (oldChapters.size * history.percent).toInt()
+			index = (oldChapters.lastIndex * history.percent).toInt()
 		}
 		val newChapters = checkNotNull(newManga.chapters).groupBy { it.branch }
 		val newBranch = if (newChapters.containsKey(branch)) {