Different behavior between Xalan & MSXSL.exe

I have the following XML sample.
<test>
<test1 attr1="kkk"/>
<test2 attr2=""/>
</test>

When I tried to copy the content of node test
through <xsl:copy-of select="test"/>, I got
different results from Xalan and MSXSL.exe.
>From Xalan, 
I got 
<test1 attr1="kkk"/>
<test2>

But from msxsl.exe
I have
<test1 attr1="kkk"/>
<test2 attr2=""/>

Obviously, Xalan ignored the attributes have null value. 
Did anybody know how to disable this feature in Xalan? 
I suppose msxsl.exe does the right thing. <test2> and
<test2 attr2=""/> have different semantic meanings. 

thanks,
Fengrui 


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