diff --git a/csharp/extractor/Semmle.Util/ToolStatusPage.cs b/csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticMessage.cs
similarity index 77%
rename from csharp/extractor/Semmle.Util/ToolStatusPage.cs
rename to csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticMessage.cs
index a93cdec5fdf6..e8b061b29f2b 100644
--- a/csharp/extractor/Semmle.Util/ToolStatusPage.cs
+++ b/csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticMessage.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
-using System.IO;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
 using Newtonsoft.Json.Serialization;
@@ -179,64 +178,4 @@ public DiagnosticMessage(
             this.PlaintextMessage = plaintextMessage;
         }
     }
-
-    /// <summary>
-    /// Provides the ability to write diagnostic messages to some output.
-    /// </summary>
-    public interface IDiagnosticsWriter : IDisposable
-    {
-        /// <summary>
-        /// Adds <paramref name="message" /> as a new diagnostics entry.
-        /// </summary>
-        /// <param name="message">The diagnostics entry to add.</param>
-        void AddEntry(DiagnosticMessage message);
-    }
-
-    /// <summary>
-    /// A wrapper around an underlying <see cref="StreamWriter" /> which allows
-    /// <see cref="DiagnosticMessage" /> objects to be serialized to it.
-    /// </summary>
-    public sealed class DiagnosticsStream : IDiagnosticsWriter, IDisposable
-    {
-        private readonly JsonSerializer serializer;
-        private readonly StreamWriter writer;
-
-        /// <summary>
-        /// Initialises a new <see cref="DiagnosticsStream" /> for a file at <paramref name="path" />.
-        /// </summary>
-        /// <param name="path">The path to the file that should be created.</param>
-        public DiagnosticsStream(string path)
-        {
-            this.writer = File.CreateText(path);
-
-            var contractResolver = new DefaultContractResolver
-            {
-                NamingStrategy = new CamelCaseNamingStrategy()
-            };
-
-            serializer = new JsonSerializer
-            {
-                ContractResolver = contractResolver,
-                NullValueHandling = NullValueHandling.Ignore
-            };
-        }
-
-        /// <summary>
-        /// Adds <paramref name="message" /> as a new diagnostics entry.
-        /// </summary>
-        /// <param name="message">The diagnostics entry to add.</param>
-        public void AddEntry(DiagnosticMessage message)
-        {
-            serializer.Serialize(writer, message);
-            writer.Flush();
-        }
-
-        /// <summary>
-        /// Releases all resources used by the <see cref="DiagnosticsStream" /> object.
-        /// </summary>
-        public void Dispose()
-        {
-            writer.Dispose();
-        }
-    }
 }
diff --git a/csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticsStream.cs b/csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticsStream.cs
new file mode 100644
index 000000000000..1ac2edc5602c
--- /dev/null
+++ b/csharp/extractor/Semmle.Util/ToolStatusPage/DiagnosticsStream.cs
@@ -0,0 +1,55 @@
+using System;
+using System.IO;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
+
+namespace Semmle.Util
+{
+    /// <summary>
+    /// A wrapper around an underlying <see cref="StreamWriter" /> which allows
+    /// <see cref="DiagnosticMessage" /> objects to be serialized to it.
+    /// </summary>
+    public sealed class DiagnosticsStream : IDiagnosticsWriter, IDisposable
+    {
+        private readonly JsonSerializer serializer;
+        private readonly StreamWriter writer;
+
+        /// <summary>
+        /// Initialises a new <see cref="DiagnosticsStream" /> for a file at <paramref name="path" />.
+        /// </summary>
+        /// <param name="path">The path to the file that should be created.</param>
+        public DiagnosticsStream(string path)
+        {
+            this.writer = File.CreateText(path);
+
+            var contractResolver = new DefaultContractResolver
+            {
+                NamingStrategy = new CamelCaseNamingStrategy()
+            };
+
+            serializer = new JsonSerializer
+            {
+                ContractResolver = contractResolver,
+                NullValueHandling = NullValueHandling.Ignore
+            };
+        }
+
+        /// <summary>
+        /// Adds <paramref name="message" /> as a new diagnostics entry.
+        /// </summary>
+        /// <param name="message">The diagnostics entry to add.</param>
+        public void AddEntry(DiagnosticMessage message)
+        {
+            serializer.Serialize(writer, message);
+            writer.Flush();
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="DiagnosticsStream" /> object.
+        /// </summary>
+        public void Dispose()
+        {
+            writer.Dispose();
+        }
+    }
+}
diff --git a/csharp/extractor/Semmle.Util/ToolStatusPage/IDiagnosticsWriter.cs b/csharp/extractor/Semmle.Util/ToolStatusPage/IDiagnosticsWriter.cs
new file mode 100644
index 000000000000..eda3dbb41d83
--- /dev/null
+++ b/csharp/extractor/Semmle.Util/ToolStatusPage/IDiagnosticsWriter.cs
@@ -0,0 +1,16 @@
+using System;
+
+namespace Semmle.Util
+{
+    /// <summary>
+    /// Provides the ability to write diagnostic messages to some output.
+    /// </summary>
+    public interface IDiagnosticsWriter : IDisposable
+    {
+        /// <summary>
+        /// Adds <paramref name="message" /> as a new diagnostics entry.
+        /// </summary>
+        /// <param name="message">The diagnostics entry to add.</param>
+        void AddEntry(DiagnosticMessage message);
+    }
+}