diff --git a/Fltk/GUI.cpp b/Fltk/GUI.cpp
index 0318ce640b3788bacdd34053b06d606a13a9b133..4c9fb61cb16db4f943b841fd2b7c2aace7f32056 100644
--- a/Fltk/GUI.cpp
+++ b/Fltk/GUI.cpp
@@ -4285,6 +4285,7 @@ void GUI::create_message_window(bool redraw_only)
 
 void GUI::add_message(const char *msg)
 {
+  // remove \n, \t, \r
   std::string str(msg);
   for(unsigned int i = 0; i < str.size(); i++)
     if(str[i] == '\n' || str[i] == '\t' || str[i] == '\r') str[i] = ' ';