diff --git a/app/src/main/java/org/koitharu/kotatsu/local/data/MangaIndex.kt b/app/src/main/java/org/koitharu/kotatsu/local/data/MangaIndex.kt
index 9ace45a82..eb216a140 100644
--- a/app/src/main/java/org/koitharu/kotatsu/local/data/MangaIndex.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/local/data/MangaIndex.kt
@@ -84,7 +84,7 @@ class MangaIndex(source: String?) {
 
 	fun getCoverEntry(): String? = json.getStringOrNull("cover_entry")
 
-	fun addChapter(chapter: MangaChapter) {
+	fun addChapter(chapter: MangaChapter, filename: String?) {
 		val chapters = json.getJSONObject("chapters")
 		if (!chapters.has(chapter.id.toString())) {
 			val jo = JSONObject()
@@ -95,6 +95,7 @@ class MangaIndex(source: String?) {
 			jo.put("scanlator", chapter.scanlator)
 			jo.put("branch", chapter.branch)
 			jo.put("entries", "%08d_%03d\\d{3}".format(chapter.branch.hashCode(), chapter.number))
+			jo.put("file", filename)
 			chapters.put(chapter.id.toString(), jo)
 		}
 	}
@@ -103,6 +104,10 @@ class MangaIndex(source: String?) {
 		return json.getJSONObject("chapters").remove(id.toString()) != null
 	}
 
+	fun getChapterFileName(chapterId: Long): String? {
+		return json.optJSONObject("chapters")?.optJSONObject(chapterId.toString())?.getStringOrNull("file")
+	}
+
 	fun setCoverEntry(name: String) {
 		json.put("cover_entry", name)
 	}
diff --git a/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaDirOutput.kt b/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaDirOutput.kt
index 0948d37af..4e97b188e 100644
--- a/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaDirOutput.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaDirOutput.kt
@@ -54,7 +54,7 @@ class LocalMangaDirOutput(
 		runInterruptible(Dispatchers.IO) {
 			output.put(name, file)
 		}
-		index.addChapter(chapter)
+		index.addChapter(chapter, chapterFileName(chapter))
 	}
 
 	override suspend fun flushChapter(chapter: MangaChapter): Boolean {
@@ -105,7 +105,18 @@ class LocalMangaDirOutput(
 	}
 
 	private fun chapterFileName(chapter: MangaChapter): String {
-		return "${chapter.number}_${chapter.name.toFileNameSafe()}".take(18) + ".cbz"
+		index.getChapterFileName(chapter.id)?.let {
+			return it
+		}
+		val baseName = "${chapter.number}_${chapter.name.toFileNameSafe()}".take(18)
+		var i = 0
+		while (true) {
+			val name = (if (i == 0) baseName else baseName + "_$i") + ".cbz"
+			if (!File(rootFile, name).exists()) {
+				return name
+			}
+			i++
+		}
 	}
 
 	private suspend fun flushIndex() = runInterruptible(Dispatchers.IO) {
diff --git a/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaZipOutput.kt b/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaZipOutput.kt
index 412edc40f..6c1fda62e 100644
--- a/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaZipOutput.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/local/data/output/LocalMangaZipOutput.kt
@@ -57,7 +57,7 @@ class LocalMangaZipOutput(
 		runInterruptible(Dispatchers.IO) {
 			output.put(name, file)
 		}
-		index.addChapter(chapter)
+		index.addChapter(chapter, null)
 	}
 
 	override suspend fun flushChapter(chapter: MangaChapter): Boolean = false
@@ -98,7 +98,7 @@ class LocalMangaZipOutput(
 		}
 		otherIndex?.getMangaInfo()?.chapters?.let { chapters ->
 			for (chapter in chapters) {
-				index.addChapter(chapter)
+				index.addChapter(chapter, null)
 			}
 		}
 	}