diff --git a/ultrasonic/src/main/java/org/moire/ultrasonic/domain/Indexes.java b/ultrasonic/src/main/java/org/moire/ultrasonic/domain/Indexes.java
deleted file mode 100644
index 81fbdd86..00000000
--- a/ultrasonic/src/main/java/org/moire/ultrasonic/domain/Indexes.java
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- This file is part of Subsonic.
-
- Subsonic is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- Subsonic is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with Subsonic.  If not, see <http://www.gnu.org/licenses/>.
-
- Copyright 2009 (C) Sindre Mehus
- */
-package org.moire.ultrasonic.domain;
-
-import java.io.Serializable;
-import java.util.List;
-
-/**
- * @author Sindre Mehus
- */
-public class Indexes implements Serializable
-{
-
-	/**
-	 *
-	 */
-	private static final long serialVersionUID = 8156117238598414701L;
-	private final long lastModified;
-	private final String ignoredArticles;
-	private final List<org.moire.ultrasonic.domain.Artist> shortcuts;
-	private final List<org.moire.ultrasonic.domain.Artist> artists;
-
-	public Indexes(long lastModified, String ignoredArticles, List<Artist> shortcuts, List<Artist> artists)
-	{
-		this.lastModified = lastModified;
-		this.ignoredArticles = ignoredArticles;
-		this.shortcuts = shortcuts;
-		this.artists = artists;
-	}
-
-	public long getLastModified()
-	{
-		return lastModified;
-	}
-
-	public List<org.moire.ultrasonic.domain.Artist> getShortcuts()
-	{
-		return shortcuts;
-	}
-
-	public List<org.moire.ultrasonic.domain.Artist> getArtists()
-	{
-		return artists;
-	}
-
-	public String getIgnoredArticles()
-	{
-		return ignoredArticles;
-	}
-}
\ No newline at end of file
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/APIIndexesConverter.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/APIIndexesConverter.kt
index fbecc194..4f72202a 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/APIIndexesConverter.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/APIIndexesConverter.kt
@@ -7,7 +7,9 @@ import org.moire.ultrasonic.api.subsonic.models.Index
 import org.moire.ultrasonic.api.subsonic.models.Indexes as APIIndexes
 
 fun APIIndexes.toDomainEntity(): Indexes = Indexes(this.lastModified, this.ignoredArticles,
-        this.shortcutList.map { it.toDomainEntity() }, this.indexList.foldIndexToArtistList())
+        this.shortcutList.map { it.toDomainEntity() }.toMutableList(),
+        this.indexList.foldIndexToArtistList().toMutableList()
+)
 
 private fun List<Index>.foldIndexToArtistList(): List<Artist> = this.fold(listOf(), {
     acc, index -> acc + index.artists.map { it.toDomainEntity() }
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/Indexes.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/Indexes.kt
new file mode 100644
index 00000000..48711c2d
--- /dev/null
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/domain/Indexes.kt
@@ -0,0 +1,14 @@
+package org.moire.ultrasonic.domain
+
+import java.io.Serializable
+
+data class Indexes(
+        val lastModified: Long,
+        val ignoredArticles: String,
+        val shortcuts: MutableList<Artist> = mutableListOf(),
+        val artists: MutableList<Artist> = mutableListOf()
+) : Serializable {
+    companion object {
+        private const val serialVersionUID = 8156117238598414701L
+    }
+}
diff --git a/ultrasonic/src/test/kotlin/org/moire/ultrasonic/domain/APIPlaylistConverterTest.kt b/ultrasonic/src/test/kotlin/org/moire/ultrasonic/domain/APIPlaylistConverterTest.kt
index 6179f7cc..3d35339a 100644
--- a/ultrasonic/src/test/kotlin/org/moire/ultrasonic/domain/APIPlaylistConverterTest.kt
+++ b/ultrasonic/src/test/kotlin/org/moire/ultrasonic/domain/APIPlaylistConverterTest.kt
@@ -44,7 +44,7 @@ class APIPlaylistConverterTest {
             name `should equal to` entity.name
             comment `should equal to` entity.comment
             owner `should equal to` entity.owner
-            public `should equal to` entity.public
+            public `should equal` entity.public
             songCount `should equal to` entity.songCount.toString()
             created `should equal to` playlistDateFormat.format(entity.created?.time)
         }