diff --git a/include/wx/defs.h b/include/wx/defs.h
index 74e04440bf..63a0822e76 100644
--- a/include/wx/defs.h
+++ b/include/wx/defs.h
@@ -376,6 +376,7 @@ typedef int wxWindowID;
     #endif
 
     #define WXMAKINGDLL_CORE
+    #define WXMAKINGDLL_HTML
 #endif // WXMAKINGDLL
 
 #ifdef WXUSINGDLL