Saxon

I have run into a quirk when using the @serialize@ function with serialization options where the @html-version@ is set to the integer @5@ e.g.

serialize(
  
    
      <title>Test</title>
    
    
      
This is a test.
This is a test.
    
  ,
  map {
    'method' : 'html',
    'indent' : true(),
    'html-version' : 5
  }
)

gives a (tested with @Saxon-HE 9.8.0.12J@ from the command line) ClassCastException

java.lang.ClassCastException: net.sf.saxon.value.Int64Value cannot be cast to net.sf.saxon.value.BigDecimalValue
        at net.sf.saxon.functions.Serialize.setSerializationParams(Serialize.java:365)
        at net.sf.saxon.functions.Serialize.evalSerialize(Serialize.java:485)
        at net.sf.saxon.functions.Serialize.call(Serialize.java:441)
        at net.sf.saxon.functions.Serialize.call(Serialize.java:49)
        at net.sf.saxon.expr.FunctionCall.iterate(FunctionCall.java:547)
        at net.sf.saxon.expr.Expression.process(Expression.java:930)
        at net.sf.saxon.query.XQueryExpression.run(XQueryExpression.java:411)
        at net.sf.saxon.s9api.XQueryEvaluator.run(XQueryEvaluator.java:370)
        at net.sf.saxon.Query.runQuery(Query.java:955)
        at net.sf.saxon.Query.doQuery(Query.java:456)
        at net.sf.saxon.Query.main(Query.java:107)

Granted, the spec on @serialize@ declares the @html-version@ parameter as type @xs:decimal@ but as that spec also says

Subtype Substitution: A derived type may substitute for its base type. In particular, xs:integer may be used where xs:decimal is expected.

I would expect the integer @5@ to be accepted.