diff --git a/monitor/bot-status.py b/monitor/bot-status.py
index a030d3e..6e37def 100755
--- a/monitor/bot-status.py
+++ b/monitor/bot-status.py
@@ -110,10 +110,12 @@
                     status["first_fail_url"] = "{}/builds/{}".format(
                         agent_url, first_fail["number"]
                     )
-                    fail_since = int(datetime.now().timestamp()) - int(
-                        first_fail["complete_at"]
-                    )
-                    status["fail_since"] = timedelta(seconds=fail_since)
+                    # Occasionaly we find a finished build without complete_at,
+                    # it may be an intermitent issue on Buildbot's side.
+                    complete_at = first_fail.get("complete_at")
+                    if complete_at is not None:
+                      fail_since = int(datetime.now().timestamp()) - int(complete_at)
+                      status["fail_since"] = timedelta(seconds=fail_since)
                     break
                 first_fail = build
             else: