diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
index 4da6a7f3ae..439bc15243 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
@@ -6,6 +6,8 @@ using Avalonia.Utilities;
 using System;
 using System.Collections.Generic;
 
+#nullable enable
+
 namespace Avalonia.Markup.Parsers
 {
     internal enum SourceMode
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/PropertyPathGrammar.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/PropertyPathGrammar.cs
index 8e0a40ccf4..9b67f9c7bc 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/PropertyPathGrammar.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/PropertyPathGrammar.cs
@@ -3,6 +3,8 @@ using System.Collections.Generic;
 using Avalonia.Data.Core;
 using Avalonia.Utilities;
 
+#nullable enable
+
 namespace Avalonia.Markup.Parsers
 {
 #if !BUILDTASK
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
index d821a04d93..af307ca1ac 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
@@ -4,6 +4,8 @@ using System.Linq;
 using Avalonia.Data.Core;
 using Avalonia.Utilities;
 
+#nullable enable
+
 // Don't need to override GetHashCode as the ISyntax objects will not be stored in a hash; the 
 // only reason they have overridden Equals methods is for unit testing.
 #pragma warning disable 659