FOP throws a validation exception when an fo:table-row contains a marker as its first child

XSL-FO 1.1 explicitly states [1] that an fo:table-row may have zero or more fo:marker elements as its initial children, yet FOP throws a validation exception in such a situation:
org.apache.fop.fo.ValidationException: "

marker" is not a valid child of "fo:table-row"! (See position 23:60)

[1] http://www.w3.org/TR/xsl11/#fo_table-row