diff --git a/include/wx/string.h b/include/wx/string.h
index 03c21a7acf..ee63cf915c 100644
--- a/include/wx/string.h
+++ b/include/wx/string.h
@@ -3485,7 +3485,7 @@ private:
 
   void DoUngetWriteBuf(size_t nLen)
   {
-      wxSTRING_SET_CACHED_LENGTH(nLen);
+      wxSTRING_INVALIDATE_CACHE();
 
       m_impl.DoUngetWriteBuf(nLen);
   }