diff --git a/mainloop.cpp b/mainloop.cpp
index 5cae0d3..4db0940 100644
--- a/mainloop.cpp
+++ b/mainloop.cpp
@@ -310,7 +310,7 @@
     // Check sysfs for available sensors.
     auto sensors = std::make_unique<SensorSet>(_hwmonRoot + '/' + _instance);
 
-    for (auto& i : *sensors)
+    for (const auto& i : *sensors)
     {
         auto object = getObject(i);
         if (object)
@@ -475,7 +475,7 @@
     }
 
     // Remove any sensors marked for removal
-    for (auto& i : rmSensors)
+    for (const auto& i : rmSensors)
     {
         state.erase(i.first);
     }