diff --git a/pingtop.py b/pingtop.py
index 0ccafa5..72cc469 100644
--- a/pingtop.py
+++ b/pingtop.py
@@ -211,6 +211,11 @@ def __init__(self, packetsize, *args, **kwargs):
 def global_input(key):
     global current_sort_column
     global sort_reverse
+
+    # keyboard input only
+    if not isinstance(key, str):
+        return
+
     if key in ("q", "Q", "^C"):
         event.clear()
         raise urwid.ExitMainLoop()