Xamarin Studio: Rebuild project error with error : The "DebugType" parameter is not supported by the "XamlCTask" task

I have managed to rebuild the project by remove the line DebugType = "$(DebugType)" in the xml file below. What does this line really do and why it can fix my problem. I have the error because I pulling the new code from source tree.

<Target Name="XamlC">
    <XamlCTask
        Assembly = "$(IntermediateOutputPath)$(TargetFileName)"
        ReferencePath = "@(ReferencePath)"
        Verbosity = "2"
        OptimizeIL = "true"
        DebugSymbols = "$(DebugSymbols)"
        />
</Target>