diff -rupN --no-dereference gmsh-4.5.6-source/Fltk/helpWindow.cpp gmsh-4.5.6-source-new/Fltk/helpWindow.cpp
--- gmsh-4.5.6-source/Fltk/helpWindow.cpp	2020-03-30 21:37:17.637647264 +0200
+++ gmsh-4.5.6-source-new/Fltk/helpWindow.cpp	2020-03-30 21:37:17.883647266 +0200
@@ -3,6 +3,12 @@
 // See the LICENSE.txt file for license information. Please report all
 // issues on https://gitlab.onelab.info/gmsh/gmsh/issues.
 
+#include "GmshConfig.h"
+
+#if defined(HAVE_MED)
+#include <med/med.h>
+#endif
+
 #include <sstream>
 #include <algorithm>
 #include <string>
@@ -13,7 +19,6 @@
 #include <FL/Fl_Check_Button.H>
 #include <FL/Fl_Input.H>
 #include <FL/Fl_Color_Chooser.H>
-#include "GmshConfig.h"
 #include "FlGui.h"
 #include "inputValue.h"
 #include "helpWindow.h"