diff --git a/src/Lucene.Net.Core/Index/IndexWriter.cs b/src/Lucene.Net.Core/Index/IndexWriter.cs
index fbedd45826..7c4627b4a0 100644
--- a/src/Lucene.Net.Core/Index/IndexWriter.cs
+++ b/src/Lucene.Net.Core/Index/IndexWriter.cs
@@ -904,7 +904,7 @@ public IndexWriter(Directory d, IndexWriterConfig conf)
                         // points.
                         if (commit.Directory != directory)
                         {
-                            throw new System.ArgumentException("IndexCommit's directory doesn't match my directory");
+                            throw new ArgumentException(string.Format("IndexCommit's directory doesn't match my directory (mine: {0}, commit's: {1})", directory, commit.Directory));
                         }
                         SegmentInfos oldInfos = new SegmentInfos();
                         oldInfos.Read(directory, commit.SegmentsFileName);
@@ -2861,7 +2861,7 @@ internal virtual void CheckpointNoSIS()
 
         /// <summary>
         /// Called internally if any index state has changed. </summary>
-        internal virtual void Changed()
+        internal void Changed()
         {
             lock (this)
             {
diff --git a/src/Lucene.Net.TestFramework/Util/VirtualMethod.cs b/src/Lucene.Net.TestFramework/Util/VirtualMethod.cs
index 319efaaac6..7cc661b5ec 100644
--- a/src/Lucene.Net.TestFramework/Util/VirtualMethod.cs
+++ b/src/Lucene.Net.TestFramework/Util/VirtualMethod.cs
@@ -49,7 +49,7 @@ namespace Lucene.Net.Util
     ///  final boolean isDeprecatedMethodOverridden =
     ///   VirtualMethod.compareImplementationDistance(this.getClass(), oldMethod, newMethod) > 0
     /// </pre>
-    /// <p><seealso cref="getImplementationDistance"/> returns the distance of the subclass that overrides this method.
+    /// <p><seealso cref="GetImplementationDistance"/> returns the distance of the subclass that overrides this method.
     /// The one with the larger distance should be used preferable.
     /// this way also more complicated method rename scenarios can be handled
     /// (think of 2.9 {@code TokenStream} deprecations).</p>
@@ -67,9 +67,9 @@ public sealed class VirtualMethod<C>
 
         /// <summary>
         /// Creates a new instance for the given {@code baseClass} and method declaration. </summary>
-        /// <exception cref="UnsupportedOperationException"> if you create a second instance of the same
+        /// <exception cref="InvalidOperationException"> if you create a second instance of the same
         ///  {@code baseClass} and method declaration combination. this enforces the singleton status. </exception>
-        /// <exception cref="IllegalArgumentException"> if {@code baseClass} does not declare the given method. </exception>
+        /// <exception cref="ArgumentException"> if {@code baseClass} does not declare the given method. </exception>
         public VirtualMethod(Type baseClass, string method, params Type[] parameters)
         {
             this.BaseClass = baseClass;