diff --git a/include/wx/defs.h b/include/wx/defs.h
index 79f795e0ad..6a9e046661 100644
--- a/include/wx/defs.h
+++ b/include/wx/defs.h
@@ -170,6 +170,7 @@
     #endif /*  compilers */
 #endif /*  HAVE_BOOL */
 
+#if !defined(__MWERKS__) || !defined(true)
 #if !defined(HAVE_BOOL) && !defined(bool) && !defined(VMS)
     /*  NB: of course, this doesn't replace the standard type, because, for */
     /*      example, overloading based on bool/int parameter doesn't work and */
@@ -185,6 +186,7 @@
     #define true ((bool)1)
     #define false ((bool)0)
 #endif
+#endif
 
 /*  for backwards compatibility, also define TRUE and FALSE */
 /*  */