Saxon

When using one iterate inside another iterate, I'm getting a java.lang.NullPointerException.

A repro script code is:

<xsl:template match="/">

	<xsl:iterate select="//row">

		<xsl:variable name="days.left" as="xs:integer">

			<xsl:iterate select="following-sibling::row">

				<xsl:param name="days" select="0"/>

				<xsl:on-completion>

					<xsl:sequence select="$days"/>

				</xsl:on-completion>

				<xsl:next-iteration>

					<xsl:with-param name="days" select="$days + 1"/>

				</xsl:next-iteration>

			</xsl:iterate>

		</xsl:variable>

		<day date="{@Date}" days.left="{$days.left}"/>

	</xsl:iterate>

</xsl:template>

I'm getting the error regardless of whether the internal iterate is inside a variable or not.