diff --git a/src/Workspaces/Core/Portable/Options/OptionServiceFactory.cs b/src/Workspaces/Core/Portable/Options/OptionServiceFactory.cs
index cf6b473519458658674ee66ef08c44aa5a7a1622..0e13ddad27f84953945b6dc138253e7181afa80f 100644
--- a/src/Workspaces/Core/Portable/Options/OptionServiceFactory.cs
+++ b/src/Workspaces/Core/Portable/Options/OptionServiceFactory.cs
@@ -206,7 +206,7 @@ public DocumentSpecificOptionSet(List<IDocumentOptions> documentOptions, OptionS
 
                 public override OptionSet WithChangedOption(OptionKey optionAndLanguage, object? value)
                 {
-                    return new DocumentSpecificOptionSet(_documentOptions, _underlyingOptions, _values.Add(optionAndLanguage, value));
+                    return new DocumentSpecificOptionSet(_documentOptions, _underlyingOptions, _values.SetItem(optionAndLanguage, value));
                 }
 
                 internal override IEnumerable<OptionKey> GetChangedOptions(OptionSet optionSet)