I am trying to work out how to implement plugins but I am getting the following error:

Qt Code: 
  1. In file included from helloworld_plugin.h:1,
  2.                  from helloworld_plugin.cpp:1:
  3. ../plugins.h:12: error: expected identifier before string constant
  4. ../plugins.h:12: error: expected `,' or `...' before string constant
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This is the piece of code in question:

Qt Code: 
  1. #ifndef INTERFACES_H
  2. #define INTERFACES_H
  3.  
  4. class QString;
  5.  
  6. class PluginInterface
  7. {
  8.     public:
  9.         virtual QString getString() = 0;
  10. };
  11.  
  12. Q_DECLARE_INTERFACE(PluginInterface, "PluginExample.PluginInterface/1.0")
  13.  
  14. #endif
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What am I doing wrong?

Qt4.1.4 and MinGw on winxp

Thanks,
Royce