diff --git a/src/NuGetMirror/MirrorUtility.cs b/src/NuGetMirror/MirrorUtility.cs
index 4c876d9..94aa729 100644
--- a/src/NuGetMirror/MirrorUtility.cs
+++ b/src/NuGetMirror/MirrorUtility.cs
@@ -9,34 +9,32 @@
 
 namespace NuGetMirror
 {
-    /// <summary>
-    /// Mirror a feed to disk as a folder of nupkgs.
-    /// </summary>
     public static class MirrorUtility
     {
         private const string CursorFile = "cursor.json";
 
-        /// <summary>
-        /// cursor.json path
-        /// </summary>
         public static FileInfo GetCursorFile(DirectoryInfo root)
         {
+            ArgumentNullException.ThrowIfNull(root);
             return new FileInfo(Path.Combine(root.FullName, CursorFile));
         }
 
-        /// <summary>
-        /// Load cursor.json if it exists.
-        /// If it doesn't exist MinTime is returned.
-        /// </summary>
         public static DateTimeOffset LoadCursor(DirectoryInfo root)
         {
+            ArgumentNullException.ThrowIfNull(root);
+
             var file = GetCursorFile(root);
 
             if (file.Exists)
             {
-                var json = LoadJson(file.OpenRead());
+                using var stream = file.OpenRead();
+                var json = LoadJson(stream);
+                var cursorValue = json["cursor"]?.ToObject<string>();
 
-                return DateTimeOffset.Parse(json["cursor"]!.ToObject<string>()!, CultureInfo.InvariantCulture);
+                if (!string.IsNullOrEmpty(cursorValue))
+                {
+                    return DateTimeOffset.Parse(cursorValue, CultureInfo.InvariantCulture);
+                }
             }
 
             return DateTimeOffset.MinValue;
@@ -44,28 +42,25 @@ public static DateTimeOffset LoadCursor(DirectoryInfo root)
 
         internal static JObject LoadJson(Stream stream)
         {
-            using (var reader = new StreamReader(stream))
-            using (var jsonReader = new JsonTextReader(reader))
+            using var reader = new StreamReader(stream);
+            using var jsonReader = new JsonTextReader(reader)
             {
-                // Avoid error prone json.net date handling
-                jsonReader.DateParseHandling = DateParseHandling.None;
+                DateParseHandling = DateParseHandling.None
+            };
 
-                return JObject.Load(jsonReader);
-            }
+            return JObject.Load(jsonReader);
         }
 
-        /// <summary>
-        /// Write cursor.json to disk.
-        /// </summary>
         public static void SaveCursor(DirectoryInfo root, DateTimeOffset time)
         {
-            var file = GetCursorFile(root);
+            ArgumentNullException.ThrowIfNull(root);
 
+            var file = GetCursorFile(root);
             FileUtility.Delete(file.FullName);
 
-            var json = new JObject()
+            var json = new JObject
             {
-                { "cursor", time.ToString("o") }
+                ["cursor"] = time.ToString("o")
             };
 
             File.WriteAllText(file.FullName, json.ToString());
@@ -73,10 +68,15 @@ public static void SaveCursor(DirectoryInfo root, DateTimeOffset time)
 
         internal static void SetTempRoot(this SourceCacheContext context, string path)
         {
+            ArgumentNullException.ThrowIfNull(context);
+            ArgumentException.ThrowIfNullOrWhiteSpace(path);
+
             var folderProp = typeof(SourceCacheContext)
-               .GetField("_generatedTempFolder", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static);
+               .GetField("_generatedTempFolder",
+                   BindingFlags.Instance | BindingFlags.NonPublic)
+               ?? throw new InvalidOperationException("Field _generatedTempFolder not found");
 
-            folderProp!.SetValue(context, path);
+            folderProp.SetValue(context, path);
         }
     }
 }