diff --git a/src/common/string.cpp b/src/common/string.cpp
index 8d3c198b8d..f42bd4dfd4 100644
--- a/src/common/string.cpp
+++ b/src/common/string.cpp
@@ -1223,6 +1223,12 @@ wxString operator+(const wxChar *psz, const wxString& str)
 
 #if wxUSE_UNICODE
 
+#ifdef __MWERKS__
+#ifndef __SCHAR_MAX__
+#define __SCHAR_MAX__ 127
+#endif
+#endif
+
 wxString wxString::FromAscii(const char *ascii)
 {
     if (!ascii)