diff --git a/include/Thresholds.hpp b/include/Thresholds.hpp
index df55182..af63f72 100644
--- a/include/Thresholds.hpp
+++ b/include/Thresholds.hpp
@@ -59,8 +59,7 @@
 struct ThresholdTimer
 {
 
-    ThresholdTimer(boost::asio::io_service& ioService, Sensor* sensor) :
-        io(ioService), sensor(sensor)
+    ThresholdTimer(boost::asio::io_service& ioService) : io(ioService)
     {}
 
     bool hasActiveTimer(const Threshold& threshold, bool assert)
@@ -98,12 +97,12 @@
         }
     }
 
-    void startTimer(const Threshold& threshold, bool assert,
+    void startTimer(const std::weak_ptr<Sensor>& weakSensor,
+                    const Threshold& threshold, bool assert,
                     double assertValue);
 
     boost::asio::io_service& io;
     std::list<TimerPair> timers;
-    Sensor* sensor;
 };
 
 bool parseThresholdsFromConfig(
@@ -129,6 +128,7 @@
 void updateThresholds(Sensor* sensor);
 // returns false if a critical threshold has been crossed, true otherwise
 bool checkThresholds(Sensor* sensor);
-void checkThresholdsPowerDelay(Sensor* sensor, ThresholdTimer& thresholdTimer);
+void checkThresholdsPowerDelay(const std::weak_ptr<Sensor>& weakSensor,
+                               ThresholdTimer& thresholdTimer);
 
 } // namespace thresholds