diff --git a/gesacmonit.py b/gesacmonit.py
index 827f7edd46970d401f8a85115d53b4cff9142bb0..d012214aa862b170531031db9060dc3acfcb7308 100755
--- a/gesacmonit.py
+++ b/gesacmonit.py
@@ -769,6 +769,7 @@ class GesacMonit(multiprocessing.Process):
             # minutes from now
             if value < 0:
                 self._set_sample(point.id, new_sample)
+                self._logger.warning("Bad sample, the router was likely restarted, point {}".format(point))
                 return
             elif value > 0:
                 data[field] = value