diff --git a/alliance/src/dreal/src/GMX_event.c b/alliance/src/dreal/src/GMX_event.c
index 2d936c8b..52fb748e 100644
--- a/alliance/src/dreal/src/GMX_event.c
+++ b/alliance/src/dreal/src/GMX_event.c
@@ -95,6 +95,7 @@
      <EnterWindow>:   CallbackEvent(  3 )\n\
      <LeaveWindow>:   CallbackEvent(  4 )\n\
      <Key>osfUp:      CallbackEvent(  5 )\n\
+     <Btn4Down>:      CallbackEvent(  5 )\n\
      <Key>osfDown:    CallbackEvent(  6 )\n\
      <Btn5Down>:      CallbackEvent(  6 )\n\
      <Key>osfLeft:    CallbackEvent(  7 )\n\