diff --git a/app/src/main/java/eu/kanade/tachiyomi/source/LocalSource.kt b/app/src/main/java/eu/kanade/tachiyomi/source/LocalSource.kt
index b6116c476..506ef910f 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/source/LocalSource.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/source/LocalSource.kt
@@ -28,13 +28,15 @@ import timber.log.Timber
 
 class LocalSource(private val context: Context) : CatalogueSource {
     companion object {
+        const val ID = 0L
         const val HELP_URL = "https://tachiyomi.org/help/guides/reading-local-manga/"
 
         private const val COVER_NAME = "cover.jpg"
+        private val SUPPORTED_ARCHIVE_TYPES = setOf("zip", "rar", "cbr", "cbz", "epub")
+
         private val POPULAR_FILTERS = FilterList(OrderBy())
         private val LATEST_FILTERS = FilterList(OrderBy().apply { state = Filter.Sort.Selection(1, false) })
         private val LATEST_THRESHOLD = TimeUnit.MILLISECONDS.convert(7, TimeUnit.DAYS)
-        const val ID = 0L
 
         fun updateCover(context: Context, manga: SManga, input: InputStream): File? {
             val dir = getBaseDirectories(context).firstOrNull()
@@ -73,9 +75,12 @@ class LocalSource(private val context: Context) : CatalogueSource {
         val baseDirs = getBaseDirectories(context)
 
         val time = if (filters === LATEST_FILTERS) System.currentTimeMillis() - LATEST_THRESHOLD else 0L
-        var mangaDirs = baseDirs.mapNotNull { it.listFiles()?.toList() }
+        var mangaDirs = baseDirs
+            .asSequence()
+            .mapNotNull { it.listFiles()?.toList() }
             .flatten()
-            .filter { it.isDirectory && if (time == 0L) it.name.contains(query, ignoreCase = true) else it.lastModified() >= time }
+            .filter { it.isDirectory }
+            .filter { if (time == 0L) it.name.contains(query, ignoreCase = true) else it.lastModified() >= time }
             .distinctBy { it.name }
 
         val state = ((if (filters.isEmpty()) POPULAR_FILTERS else filters)[0] as OrderBy).state
@@ -132,13 +137,15 @@ class LocalSource(private val context: Context) : CatalogueSource {
                 }
             }
         }
-        return Observable.just(MangasPage(mangas, false))
+
+        return Observable.just(MangasPage(mangas.toList(), false))
     }
 
     override fun fetchLatestUpdates(page: Int) = fetchSearchManga(page, "", LATEST_FILTERS)
 
     override fun fetchMangaDetails(manga: SManga): Observable<SManga> {
         getBaseDirectories(context)
+            .asSequence()
             .mapNotNull { File(it, manga.url).listFiles()?.toList() }
             .flatten()
             .firstOrNull { it.extension == "json" }
@@ -154,6 +161,7 @@ class LocalSource(private val context: Context) : CatalogueSource {
                     ?: manga.genre
                 manga.status = json["status"]?.asInt ?: manga.status
             }
+
         return Observable.just(manga)
     }
 
@@ -204,8 +212,8 @@ class LocalSource(private val context: Context) : CatalogueSource {
         var chapterNameIndex = 0
         var mangaTitleIndex = 0
         while (chapterNameIndex < chapterName.length && mangaTitleIndex < mangaTitle.length) {
-            val chapterChar = chapterName.get(chapterNameIndex)
-            val mangaChar = mangaTitle.get(mangaTitleIndex)
+            val chapterChar = chapterName[chapterNameIndex]
+            val mangaChar = mangaTitle[mangaTitleIndex]
             if (!chapterChar.equals(mangaChar, true)) {
                 val invalidChapterChar = !chapterChar.isLetterOrDigit() && !chapterChar.isWhitespace()
                 val invalidMangaChar = !mangaChar.isLetterOrDigit() && !mangaChar.isWhitespace()
@@ -235,7 +243,7 @@ class LocalSource(private val context: Context) : CatalogueSource {
     }
 
     private fun isSupportedFile(extension: String): Boolean {
-        return extension.toLowerCase() in setOf("zip", "rar", "cbr", "cbz", "epub")
+        return extension.toLowerCase() in SUPPORTED_ARCHIVE_TYPES
     }
 
     fun getFormat(chapter: SChapter): Format {
@@ -269,8 +277,8 @@ class LocalSource(private val context: Context) : CatalogueSource {
         return when (val format = getFormat(chapter)) {
             is Format.Directory -> {
                 val entry = format.file.listFiles()
-                    .sortedWith(Comparator<File> { f1, f2 -> f1.name.compareToCaseInsensitiveNaturalOrder(f2.name) })
-                    .find { !it.isDirectory && ImageUtil.isImage(it.name) { FileInputStream(it) } }
+                    ?.sortedWith(Comparator<File> { f1, f2 -> f1.name.compareToCaseInsensitiveNaturalOrder(f2.name) })
+                    ?.find { !it.isDirectory && ImageUtil.isImage(it.name) { FileInputStream(it) } }
 
                 entry?.let { updateCover(context, manga, it.inputStream()) }
             }