diff --git a/include/wx/defs.h b/include/wx/defs.h
index 897d1addb3..f87619fa48 100644
--- a/include/wx/defs.h
+++ b/include/wx/defs.h
@@ -186,10 +186,13 @@
         #ifndef WX_TRUE_DEFINED
             #undef TRUE
             #undef FALSE
-            #define TRUE  ((bool)1)
-            #define FALSE ((bool)0)
         #endif
     #endif
+
+    #ifndef TRUE
+        #define TRUE  ((bool)1)
+        #define FALSE ((bool)0)
+    #endif
 #else // !__cplusplus
     // the definitions above don't work for C sources
     #ifndef TRUE