unmatched type specification error

Following the ML-Yacc user guide, I created a file glue.sml with the 
following content:

structure SlpLrVals = SlpLrValsFun(structure Token = LrParser.Token);
structure SlpLex = SlpLexFun(structure Tokens = SlpLrVals.Tokens);
structure SlpParser = JoinWithArg(
        structure ParserData = SlpLrVals.ParserData
        structure Lex=SlpLex
        structure LrParser = LrParser);

Compiling my parser, I get the following error:

glue.sml:3.23-6.33 Error: unmatched type specification: arg

Any idea what is wrong with this code?

TIA.

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