Prefix is not mapped to a namespace

Hello All:

  I have a incoming XML with ns0 name space. I had to anticipate it so I put in the declaration xmlns:ns0 = "http://XXXX-myxml.com"  in the xsl:stylesheet.

  But when I run this scenario. It throw exception at run time. With below error message

"

XCE001 Nested exception: com.sap.b1i.bizprocessor.BizProcException: BPE001 Nested exception: com.sap.b1i.utilities.UtilException: UTE001 Nested exception: javax.xml.transform.TransformerConfigurationException: Could not load stylesheet.com.sap.engine.lib.xml.util.NestedException: Could not load XSLWhen. Stylesheet: null, element: <xsl:when xmlns:xsl="http://www.w3.org/1999/XSL/Transform" test="$msg/ns0:PriceList">PriceList</xsl:when> -> com.sap.engine.lib.xml.util.NestedException: Prefix not mapped: ns0 -> java.lang.Exception: XMLParser: Prefix 'ns0' is not mapped to a namespace

Thank You!