diff --git a/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs b/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
index 1e885aad6e..3ee1c757f2 100644
--- a/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
+++ b/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
@@ -16,7 +16,7 @@ namespace Emby.Server.Implementations.Library.Resolvers.Books
 {
     public class BookResolver : ItemResolver<Book>
     {
-        private readonly string[] _validExtensions = { ".azw", ".azw3", ".cb7", ".cbr", ".cbt", ".cbz", ".epub", ".mobi", ".pdf" };
+        private readonly string[] _validExtensions = { ".azw", ".azw3", ".cb7", ".cbr", ".cbt", ".cbz", ".epub", ".mobi", ".pdf", ".m4b", ".m4a", ".aac", ".flac", ".mp3", ".opus" };
 
         protected override Book Resolve(ItemResolveArgs args)
         {