XSL Parameter doesn't work in a choose?!

RenderArticleList.xslt

  <xsl:template name="renderArticleList">
    <xsl:param name="orderByPopularity"/>
    <xsl:param name="addShowInLatestNewsList"/>
    
    <xsl:choose>

      <xsl:when test="$orderByPopularity = 'true'">
        == <xsl:value-of select="$addShowInLatestNewsList" /> ==

       <!-- 
          Displays: == == 
          
          which is wrong..
       -->

      </xsl:when>
      <xsl:otherwise>
        == <xsl:value-of select="$addShowInLatestNewsList" /> ==

        <!-- 
          Displays: == true == 

          this is the expected behaviour!
        -->
      </xsl:otherwise>
    </xsl:choose>

  </xsl:template>