diff --git a/clientgui/BOINCGUIApp.cpp b/clientgui/BOINCGUIApp.cpp
index 59c53736ee..61d084a32e 100644
--- a/clientgui/BOINCGUIApp.cpp
+++ b/clientgui/BOINCGUIApp.cpp
@@ -31,8 +31,10 @@
 #include "MainDocument.h"
 
 
+#ifdef __WXMSW__
 typedef BOOL (CALLBACK* IdleTrackerInit)();
 typedef void (CALLBACK* IdleTrackerTerm)();
+#endif
 
 
 IMPLEMENT_APP(CBOINCGUIApp)