diff --git a/concepts.hpp b/concepts.hpp
index 4a9aa9d1..f5476e1b 100644
--- a/concepts.hpp
+++ b/concepts.hpp
@@ -293,8 +293,10 @@ namespace cruft::concepts {
     template <typename T>
     concept iterable = requires (T t)
     {
-        { std::begin (t) } -> legacy_iterator;
-        { std::end   (t) } -> legacy_iterator;
+        { std::begin  (t) } -> legacy_iterator;
+        { std::end    (t) } -> legacy_iterator;
+        { std::cbegin (t) } -> legacy_iterator;
+        { std::cend   (t) } -> legacy_iterator;
     };