diff --git a/tools/mock_udpstreamer.py b/tools/mock_udpstreamer.py
index fd882ee..84dde18 100644
--- a/tools/mock_udpstreamer.py
+++ b/tools/mock_udpstreamer.py
@@ -222,8 +222,9 @@ def main():
     ap.add_argument(
         "--glitch-width",
         type=float,
-        default=0.0,
-        help="width of each injected pulse, in stream seconds",
+        default=0.002,
+        help="width of each injected pulse, in stream seconds (default 0.002 s; a zero width "
+        "silently disables the glitch even when --glitch-at is set)",
     )
     ap.add_argument(
         "--quiet-at",