diff --git a/Jellyfin.Plugin.SmartPlaylist/Lisp/Expression.cs b/Jellyfin.Plugin.SmartPlaylist/Lisp/Expression.cs
index b27f686..a5c3979 100644
--- a/Jellyfin.Plugin.SmartPlaylist/Lisp/Expression.cs
+++ b/Jellyfin.Plugin.SmartPlaylist/Lisp/Expression.cs
@@ -126,6 +126,12 @@ namespace Jellyfin.Plugin.SmartPlaylist.Lisp {
         public static Boolean operator <=(Integer a, Integer b) {
             return (a._value <= b._value) ? Boolean.TRUE : Boolean.FALSE;
         }
+        public override int GetHashCode() {
+            return base.GetHashCode();
+        }
+        public override bool Equals(object? other) {
+            return base.Equals(other);
+        }
         public static Boolean operator ==(Integer a, Integer b) {
             return (a._value == b._value) ? Boolean.TRUE : Boolean.FALSE;
         }
diff --git a/Jellyfin.Plugin.SmartPlaylist/Lisp/Interpreter.cs b/Jellyfin.Plugin.SmartPlaylist/Lisp/Interpreter.cs
index 7ad36c0..7d68941 100644
--- a/Jellyfin.Plugin.SmartPlaylist/Lisp/Interpreter.cs
+++ b/Jellyfin.Plugin.SmartPlaylist/Lisp/Interpreter.cs
@@ -7,7 +7,7 @@ namespace Jellyfin.Plugin.SmartPlaylist.Lisp {
     using FunctionLater = Func<Executor, IEnumerable<Expression>, Expression>;
 
     public interface IEnvironment<K, V> {
-        public V Get(K k);
+        public V? Get(K k);
         public void Set(K k, V v);
         public IEnvironment<K, V>? Find(K k);
         public IEnvironment<K, V> Parent(bool recursive);
@@ -377,7 +377,11 @@ namespace Jellyfin.Plugin.SmartPlaylist.Lisp {
                     if (_environment.Find(s.Name()) is not IEnvironment<string, Expression> env) {
                         throw new ApplicationException($"Could not find '{s.Name()}'");
                     }
-                    return env.Get(s.Name());
+                    var r_ = env.Get(s.Name());
+                    if (r_ is null) {
+                        throw new ApplicationException($"Could not find '{s.Name()}'");
+                    }
+                    return r_;
                 case Boolean b:
                     return b;
                 case Integer i:
diff --git a/Jellyfin.Plugin.SmartPlaylist/Store.cs b/Jellyfin.Plugin.SmartPlaylist/Store.cs
index 2fdf84d..a388125 100644
--- a/Jellyfin.Plugin.SmartPlaylist/Store.cs
+++ b/Jellyfin.Plugin.SmartPlaylist/Store.cs
@@ -14,7 +14,7 @@ namespace Jellyfin.Plugin.SmartPlaylist {
             _fileSystem = fileSystem;
         }
         private async Task<SmartPlaylistDto> LoadPlaylistAsync(string filename) {
-            var r = File.ReadAllText(filename);
+            var r = await File.ReadAllTextAsync(filename);
             if (r.Equals("")) {
                 r = "{}";
             }
@@ -46,7 +46,7 @@ namespace Jellyfin.Plugin.SmartPlaylist {
         public async Task SaveSmartPlaylistAsync(SmartPlaylistDto smartPlaylist) {
             string filename = _fileSystem.GetSmartPlaylistFilePath(smartPlaylist.Id);
             var text = new SerializerBuilder().Build().Serialize(smartPlaylist);
-            File.WriteAllText(filename, text);
+            await File.WriteAllTextAsync(filename, text);
         }
         private void DeleteSmartPlaylistById(SmartPlaylistId smartPlaylistId) {
             try {
diff --git a/Tests/Tests.cs b/Tests/Tests.cs
index 3413bf3..4052b24 100644
--- a/Tests/Tests.cs
+++ b/Tests/Tests.cs
@@ -1,5 +1,3 @@
-using Xunit;
-using Lisp_Environment = Jellyfin.Plugin.SmartPlaylist.Lisp.Environment;
 using Lisp_Boolean = Jellyfin.Plugin.SmartPlaylist.Lisp.Boolean;
 using Lisp_Object = Jellyfin.Plugin.SmartPlaylist.Lisp.Object;
 using Jellyfin.Plugin.SmartPlaylist.Lisp;