Error when open .pro file

The following error occures when opening .pro file:

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Qt Visual Studio Add-in
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The following error occured:

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

(at EnvDTE.SolutionClass.GetEnumerator()

at Nokia.QtProjectLib.ProjectImporter.ImportSolution(FileInfo mainInfo, String qtVersion))
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OK
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As a result, add-in generates incorrect .vcproj files: instead of $(QTDIR) I see _(QTDIR). For example:
AdditionalDependencies="_(QTDIR)\bin\moc.exe;draw_widget.hpp"
CommandLine="_(QTDIR)\bin\moc.exe