diff --git a/app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadCache.kt b/app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadCache.kt
index d74003c159..80dcdc7172 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadCache.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadCache.kt
@@ -126,7 +126,7 @@ class DownloadCache(
 
         val sourceDirs = getDirectoryFromPreference().listFiles().orEmpty()
             .associate { it.name to SourceDirectory(it) }.mapNotNullKeys { entry ->
-                onlineSources.find { provider.getSourceDirName(it).toLowerCase() == entry.key?.toLowerCase() }?.id
+                onlineSources.find { provider.getSourceDirName(it).equals(entry.key, ignoreCase = true) }?.id
             }
 
         val db: DatabaseHelper by injectLazy()
@@ -159,7 +159,7 @@ class DownloadCache(
      */
     private fun findManga(mangaList: List<Manga>, mangaKey: String, sourceKey: Long): Manga? {
         return mangaList.find {
-            DiskUtil.buildValidFilename(it.originalTitle).toLowerCase() == mangaKey.toLowerCase() && it.source == sourceKey
+            DiskUtil.buildValidFilename(it.originalTitle).equals(mangaKey, ignoreCase = true) && it.source == sourceKey
         }
     }
 
diff --git a/app/src/main/java/eu/kanade/tachiyomi/util/storage/DiskUtil.kt b/app/src/main/java/eu/kanade/tachiyomi/util/storage/DiskUtil.kt
index f4bab4b681..d44a63b5d7 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/util/storage/DiskUtil.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/util/storage/DiskUtil.kt
@@ -85,7 +85,7 @@ object DiskUtil {
      */
     fun buildValidFilename(origName: String): String {
         val name = origName.trim('.', ' ')
-        if (name.isNullOrEmpty()) {
+        if (name.isEmpty()) {
             return "(invalid)"
         }
         val sb = StringBuilder(name.length)