1 files changed, 7 insertions, 0 deletions

diff --git a/src/macterm.c b/src/macterm.c
index cae4172854e..e969a4b6dce 100644
--- a/src/macterm.c
+++ b/src/macterm.c
@@ -12644,6 +12644,13 @@ XTread_socket (int sd, struct input_event *bufp, int numchars, int expected)
                 Point point;
                 WindowPtr window_ptr = FrontNonFloatingWindow ();
                 struct mac_output *mwp = (mac_output *) GetWRefCon (window_ptr);
+                if (!IsValidWindowPtr (window_ptr))
+                  {
+                    SysBeep(1);
+                    UNBLOCK_INPUT;
+                    return 0;
+                  }
+
                 GetEventParameter(eventRef, kEventParamMouseWheelDelta,
                                   typeSInt32, NULL, sizeof (SInt32),
                                   NULL, &delta);