diff --git a/xsl/common.xsl b/xsl/common.xsl
index 8ef57a7fd..19e7ac412 100644
--- a/xsl/common.xsl
+++ b/xsl/common.xsl
@@ -5,7 +5,7 @@
   xmlns:atom="http://www.w3.org/2005/Atom"
   xmlns:date="http://exslt.org/dates-and-times"
   xmlns:str="http://exslt.org/strings"
-  exclude-result-prefixes="xsl atom date">
+  exclude-result-prefixes="xsl atom date str">
 
   <xsl:template match="pre">
     <pre><xsl:apply-templates/></pre>