diff --git a/include/wx/datetime.h b/include/wx/datetime.h
index 654041d61c..9f44e84143 100644
--- a/include/wx/datetime.h
+++ b/include/wx/datetime.h
@@ -17,6 +17,8 @@
     #pragma interface "datetime.h"
 #endif
 
+#include "wx/defs.h"
+
 #if wxUSE_DATETIME
 
 #include <time.h>