Simplified DocBook V1.1 informaltable HTML-style

I may have found a bug in the Simplified DocBook V1.1 DTD:
A Simplified DocBook V1.1 informaltable, HTML-style, is required to have
a caption child element.

Excerpts of sdocbook.dtd (the problem probably comes from
sdocbook-custom.dtd, but it is clearer to show it in this file):
---
<!ENTITY % informaltable.table.mdl
	"((mediaobject+|tgroup+)
          |(caption, (col*|colgroup*), thead?, tfoot?, (tbody+|tr+)))">
<!ELEMENT informaltable (%informaltable.table.mdl;) >
---