diff --git a/src/dotnet/FileSystemBase.cs b/src/dotnet/FileSystemBase.cs
index e1ce2923..a0d4e5d7 100644
--- a/src/dotnet/FileSystemBase.cs
+++ b/src/dotnet/FileSystemBase.cs
@@ -1291,7 +1291,7 @@ namespace Fsp
                 ModificationDescriptor,
                 ref ModifiedDescriptor);
         }
-        public virtual Int32 SeekableReadDirectory(
+        public Int32 SeekableReadDirectory(
             Object FileNode,
             Object FileDesc,
             String Pattern,
diff --git a/tst/memfs-dotnet/Program.cs b/tst/memfs-dotnet/Program.cs
index 5782e3a2..15a5ff04 100644
--- a/tst/memfs-dotnet/Program.cs
+++ b/tst/memfs-dotnet/Program.cs
@@ -637,7 +637,7 @@ namespace memfs
             SlowioSnooze();
 
             UInt32 BytesTransferred;
-            var Status = base.SeekableReadDirectory(FileNode0, FileDesc, Pattern, Marker, Buffer, Length, out BytesTransferred);
+            var Status = SeekableReadDirectory(FileNode0, FileDesc, Pattern, Marker, Buffer, Length, out BytesTransferred);
             Host.SendReadDirectoryResponse(RequestHint, Status, BytesTransferred);
         }
 #endif
@@ -1019,7 +1019,7 @@ namespace memfs
         }
 
 #if MEMFS_SLOWIO
-        public override int SeekableReadDirectory(
+        public override int ReadDirectory(
             Object FileNode0,
             Object FileDesc,
             String Pattern,
@@ -1037,7 +1037,7 @@ namespace memfs
                 return STATUS_PENDING;
             }
 
-            return base.SeekableReadDirectory(FileNode0, FileDesc, Pattern, Marker, Buffer, Length, out BytesTransferred);
+            return SeekableReadDirectory(FileNode0, FileDesc, Pattern, Marker, Buffer, Length, out BytesTransferred);
         }
 #endif