Could not find function: replace

[Johan Johansson]

Hi,
 
I'm trying to use the XSL 2.0 function replace() but i just got this error:
 
javax.xml.transform.TransformerException: Could not find function: replace
 
the code:
<xsl:value-of select="normalize-space(replace(../kund/brevnamn,'Å ','%A'))" />
 
Any suggestions?