[ERROR] Error in margin-left property value '0': FIXED?

Creating PDFs:

Saxon 651
XSL Stylesheets v1.62.4
FOP 0.20.5

FOP output gives me:
"[ERROR] Error in margin-left property value '0': 
org.apache.fop.fo.expr.PropertyException: No conversion defined"

A successful PDF is created.

The following changes to ../fo/pagesetup.xsl (part of the XSL Stylesheets) 
make the error go away.

Line 1367
-         <xsl:attribute name="margin-left">0</xsl:attribute>
+         <xsl:attribute name="margin-left">0pt</xsl:attribute>

Line 1600
-         <xsl:attribute name="margin-left">0</xsl:attribute>
+         <xsl:attribute name="margin-left">0pt</xsl:attribute>

If people agree this is a valid BUG/FIX, then I'll be happy to enter a 
proper bug report...

Mart