diff --git a/src/msw/thread.cpp b/src/msw/thread.cpp
index c516a161d7..e2c76f9389 100644
--- a/src/msw/thread.cpp
+++ b/src/msw/thread.cpp
@@ -371,6 +371,8 @@ private:
     wxMutex& m_mutex;
 
     wxSemaphore m_semaphore;
+
+    DECLARE_NO_COPY_CLASS(wxConditionInternal)
 };
 
 wxConditionInternal::wxConditionInternal(wxMutex& mutex)