diff --git a/src/allmydata/web/status.py b/src/allmydata/web/status.py
index 8af453c..8f7b930 100644
--- a/src/allmydata/web/status.py
+++ b/src/allmydata/web/status.py
@@ -433,7 +433,10 @@ class DownloadStatusPage(DownloadResultsRendererMixin, rend.Page):
             (start, length, requesttime, finishtime, bytes, decrypt, paused) = r_ev
             if finishtime is not None:
                 rtt = finishtime - requesttime - paused
-                speed = self.render_rate(None, 1.0 * bytes / rtt)
+                if rtt == 0:
+                    speed = "-"
+                else:
+                    speed = self.render_rate(None, 1.0 * bytes / rtt)
                 rtt = self.render_time(None, rtt)
                 decrypt = self.render_time(None, decrypt)
                 paused = self.render_time(None, paused)
@@ -459,7 +462,10 @@ class DownloadStatusPage(DownloadResultsRendererMixin, rend.Page):
             elif etype == "delivery":
                 if reqtime[0] == segnum:
                     segtime = when - reqtime[1]
-                    speed = self.render_rate(None, 1.0 * seglen / segtime)
+                    if segtime == 0:
+                        speed = "-"
+                    else:
+                        speed = self.render_rate(None, 1.0 * seglen / segtime)
                     segtime = self.render_time(None, segtime)
                 else:
                     segtime, speed = "", ""