diff --git a/source/common/common/interval_value.h b/source/common/common/interval_value.h
index 6c7e4c785d59..51697de807ac 100644
--- a/source/common/common/interval_value.h
+++ b/source/common/common/interval_value.h
@@ -26,6 +26,12 @@ template <typename T, typename Interval> class ClosedIntervalValue {
   T value_;
 };
 
+// C++17 doesn't allow templating on floating point values, otherwise that's
+// what we should do here instead of relying on a int => float implicit
+// conversion. TODO(akonradi): when Envoy is using C++20, switch these template
+// parameters to floats.
+
+// Floating point value in the range [0, 1].
 using UnitFloat = ClosedIntervalValue<float, Interval<int, 0, 1>>;
 
 } // namespace Envoy