diff --git a/src/gui_gtk_vms.h b/src/gui_gtk_vms.h
index 268c9f3..c86bd0a 100644
--- a/src/gui_gtk_vms.h
+++ b/src/gui_gtk_vms.h
@@ -74,11 +74,11 @@
  *************************************************************************
  */
 
-/* INTRINSIC.H omits proto if XtFree is defined */
-/* VMS_BEGIN_C_PLUS_PLUS */
+// INTRINSIC.H omits proto if XtFree is defined
+// VMS_BEGIN_C_PLUS_PLUS
 extern void XtFree(char*);
 extern void XTFREE(char*);
-/* VMS_END_C_PLUS_PLUS */
+// VMS_END_C_PLUS_PLUS
 
 #define _XRegisterFilterByType _XREGISTERFILTERBYTYPE
 
@@ -719,10 +719,10 @@
 ** named None. So for now hard code this is R5....
 */
 #ifndef VMS_X11R6
-/* R5 or earlier */
+// R5 or earlier
 #define _XtRegisterWindow _XTREGISTERWINDOW
 #define _XtUnregisterWindow _XTUNREGISTERWINDOW
-/* original code is fixed so we don't need this now */
+// original code is fixed so we don't need this now
 #if 0
 #define XtRegisterDrawable(display,drawable,widget) \
 {  extern void _XtRegisterWindow(Window,Widget); \
@@ -734,7 +734,7 @@
 }
 #endif
 #else
-/* R6 or later */
+// R6 or later
 #define XtRegisterDrawable XTREGISTERDRAWABLE
 #define XtUnregisterDrawable XTUNREGISTERDRAWABLE
 #endif