diff --git a/src/metric.hpp b/src/metric.hpp
index f053691..7929aac 100644
--- a/src/metric.hpp
+++ b/src/metric.hpp
@@ -22,6 +22,7 @@
     void sensorUpdated(interfaces::Sensor&, uint64_t) override;
     void sensorUpdated(interfaces::Sensor&, uint64_t, double value) override;
     LabeledMetricParameters dumpConfiguration() const override;
+    uint64_t sensorCount() const override;
 
   private:
     class CollectionData;