diff --git a/cpp/autobuilder/Semmle.Autobuild.Cpp/CppAutobuilder.cs b/cpp/autobuilder/Semmle.Autobuild.Cpp/CppAutobuilder.cs
index ee1d775e17d..e3853b44a0c 100644
--- a/cpp/autobuilder/Semmle.Autobuild.Cpp/CppAutobuilder.cs
+++ b/cpp/autobuilder/Semmle.Autobuild.Cpp/CppAutobuilder.cs
@@ -22,12 +22,7 @@ namespace Semmle.Autobuild.Cpp
 
     public class CppAutobuilder : Autobuilder<CppAutobuildOptions>
     {
-        private readonly DiagnosticClassifier classifier;
-
-        public CppAutobuilder(IBuildActions actions, CppAutobuildOptions options) : base(actions, options) =>
-            classifier = new DiagnosticClassifier();
-
-        protected override DiagnosticClassifier DiagnosticClassifier => classifier;
+        public CppAutobuilder(IBuildActions actions, CppAutobuildOptions options) : base(actions, options, new DiagnosticClassifier()) { }
 
         public override BuildScript GetBuildScript()
         {
diff --git a/csharp/autobuilder/Semmle.Autobuild.CSharp/CSharpAutobuilder.cs b/csharp/autobuilder/Semmle.Autobuild.CSharp/CSharpAutobuilder.cs
index a1126fdf12c..ed2ed4013ef 100644
--- a/csharp/autobuilder/Semmle.Autobuild.CSharp/CSharpAutobuilder.cs
+++ b/csharp/autobuilder/Semmle.Autobuild.CSharp/CSharpAutobuilder.cs
@@ -1,4 +1,4 @@
-using Semmle.Extraction.CSharp;
+using Semmle.Extraction.CSharp;
 using Semmle.Util.Logging;
 using Semmle.Autobuild.Shared;
 using Semmle.Util;
@@ -36,13 +36,8 @@ namespace Semmle.Autobuild.CSharp
 
         private readonly AutoBuildRule autoBuildRule;
 
-        protected override DiagnosticClassifier DiagnosticClassifier { get; }
-
-        public CSharpAutobuilder(IBuildActions actions, CSharpAutobuildOptions options) : base(actions, options)
-        {
+        public CSharpAutobuilder(IBuildActions actions, CSharpAutobuildOptions options) : base(actions, options, new CSharpDiagnosticClassifier()) =>
             this.autoBuildRule = new AutoBuildRule(this);
-            this.DiagnosticClassifier = new CSharpDiagnosticClassifier();
-        }
 
         public override BuildScript GetBuildScript()
         {
diff --git a/csharp/autobuilder/Semmle.Autobuild.Shared/Autobuilder.cs b/csharp/autobuilder/Semmle.Autobuild.Shared/Autobuilder.cs
index 6a3b63dc27e..2335e15015e 100644
--- a/csharp/autobuilder/Semmle.Autobuild.Shared/Autobuilder.cs
+++ b/csharp/autobuilder/Semmle.Autobuild.Shared/Autobuilder.cs
@@ -190,10 +190,11 @@ namespace Semmle.Autobuild.Shared
         /// solution file and tools.
         /// </summary>
         /// <param name="options">The command line options.</param>
-        protected Autobuilder(IBuildActions actions, TAutobuildOptions options)
+        protected Autobuilder(IBuildActions actions, TAutobuildOptions options, DiagnosticClassifier diagnosticClassifier)
         {
             Actions = actions;
             Options = options;
+            DiagnosticClassifier = diagnosticClassifier;
 
             pathsLazy = new Lazy<IEnumerable<(string, int)>>(() =>
             {
@@ -264,7 +265,7 @@ namespace Semmle.Autobuild.Shared
 
         public string DiagnosticsDir { get; }
 
-        protected abstract DiagnosticClassifier DiagnosticClassifier { get; }
+        protected DiagnosticClassifier DiagnosticClassifier { get; }
 
         private readonly ILogger logger = new ConsoleLogger(Verbosity.Info);