diff --git a/src/sensor.hpp b/src/sensor.hpp
index 17ed488..9f092c6 100644
--- a/src/sensor.hpp
+++ b/src/sensor.hpp
@@ -549,8 +549,10 @@
     // optional.
     void fillMissingThresholds()
     {
-        for (thresholds::Threshold& thisThreshold : thresholds)
+        const std::size_t thresholdsLen = thresholds.size();
+        for (std::size_t index = 0; index < thresholdsLen; ++index)
         {
+            const thresholds::Threshold& thisThreshold = thresholds[index];
             bool foundOpposite = false;
             thresholds::Direction opposite = thresholds::Direction::HIGH;
             if (thisThreshold.direction == thresholds::Direction::HIGH)