No syntax highlighting after overriding GetNextToken of a DynamicLexer

Hi,

I want to override the lexing for a specific lexical state.
So I implemented this in my Dynamic lexer. Here is a simplified version:

public override ActiproSoftware.Text.Lexing.MergableLexerResult GetNextToken(ActiproSoftware.Text.ITextBufferReader reader, ActiproSoftware.Text.Lexing.ILexicalState lexicalState)
{

if (((ActiproSoftware.Text.Lexing.Implementation.LexicalStateBase)(lexicalState)).Key != "PrimaryString")
{
return base.GetNextToken(reader, lexicalState);
}
else
{
// Custom lexing logic: 
reader.Read();
return new MergableLexerResult(MatchType.ExactMatch, new LexicalStateTokenData(lexicalState, MyScriptTokenId.PrimaryStringText));
}

} 

The token is created, but there is no syntax highlighting
The problem is that the property ClassificationType in the LexicalStateTokenData is null.
I cannot find a way to set this property; it is readonly.
(When I call the base.GetNextToken, it is working OK)

Do you have any suggestions?

Thanks and regards,

Aernout