diff --git a/Sources/Model/Album.cs b/Sources/Model/Album.cs
index 323ddb0..06380d0 100644
--- a/Sources/Model/Album.cs
+++ b/Sources/Model/Album.cs
@@ -40,7 +40,7 @@
             }
         }
 
-        private List<Title> titles = new List<Title>();
+        private readonly List<Title> titles = new List<Title>();
 
         public string ImageURL
         {
diff --git a/Sources/Model/Artiste.cs b/Sources/Model/Artiste.cs
index ab29d82..bc2a9b3 100644
--- a/Sources/Model/Artiste.cs
+++ b/Sources/Model/Artiste.cs
@@ -25,7 +25,7 @@ public class Artiste
         }
     }
 
-    private List<Album> albums = new List<Album>();
+    private readonly List<Album> albums = new List<Album>();
 
     public Artiste(string name)
     {
diff --git a/Sources/Model/InfoTitle.cs b/Sources/Model/InfoTitle.cs
index eb4e688..7a3c3b6 100644
--- a/Sources/Model/InfoTitle.cs
+++ b/Sources/Model/InfoTitle.cs
@@ -27,7 +27,7 @@ public class InfoTitle : Title
         }
     }
 
-    private List<Artiste> feat = new List<Artiste>();
+    private readonly List<Artiste> feat = new List<Artiste>();
 
     public Genre Genre { get; set; }
 
diff --git a/Sources/Model/Manager.cs b/Sources/Model/Manager.cs
index 4f8e51b..3f1de5d 100644
--- a/Sources/Model/Manager.cs
+++ b/Sources/Model/Manager.cs
@@ -12,7 +12,7 @@ public class Manager
         }
     }
 
-    private List<Album> albums = new List<Album>();
+    private readonly List<Album> albums = new List<Album>();
 
     public IEnumerable<Title> Titles
     {
@@ -22,7 +22,7 @@ public class Manager
         }
     }
 
-    private List<Title> titles = new List<Title>();
+    private readonly List<Title> titles = new List<Title>();
 
     public IEnumerable<Playlist> Playlists
     {
@@ -32,7 +32,7 @@ public class Manager
         }
     }
 
-    private List<Playlist> playlists = new List<Playlist>();
+    private readonly List<Playlist> playlists = new List<Playlist>();
 
     public Manager()
     {
diff --git a/Sources/Model/Playlist.cs b/Sources/Model/Playlist.cs
index a3882d0..afb3cd8 100644
--- a/Sources/Model/Playlist.cs
+++ b/Sources/Model/Playlist.cs
@@ -40,7 +40,7 @@ public class Playlist
         }
     }
 
-    private List<Title> titles = new List<Title>();
+    private readonly List<Title> titles = new List<Title>();
 
     public string ImageURL
     {