diff --git a/src/metric.hpp b/src/metric.hpp
index b627b4e..8b367b3 100644
--- a/src/metric.hpp
+++ b/src/metric.hpp
@@ -20,7 +20,7 @@
 
     void initialize() override;
     void deinitialize() override;
-    std::vector<MetricValue> getReadings() const override;
+    const std::vector<MetricValue>& getUpdatedReadings() override;
     void sensorUpdated(interfaces::Sensor&, Milliseconds,
                        double value) override;
     LabeledMetricParameters dumpConfiguration() const override;