diff --git a/doc/unordered/hash_traits.adoc b/doc/unordered/hash_traits.adoc
index 0abd5dcf..5a60fa82 100644
--- a/doc/unordered/hash_traits.adoc
+++ b/doc/unordered/hash_traits.adoc
@@ -36,9 +36,9 @@ this property is critical for the proper behavior of open-addressing hash contai
 
  * `false` if `Hash::is_avalanching` is not present,
  * `Hash::is_avalanching::value` if this is present and convertible at compile time to a `bool`,
- * `true` if `Hash::is_avalanching` is `void` (this usage is deprecated).
+ * `true` if `Hash::is_avalanching` is `void` (this usage is deprecated),
+ * ill-formed otherwise.
  
-The behavior is undefined if none of the three cases above is met.
 Users can then declare a hash function `Hash` as avalanching either by embedding an appropriate `is_avalanching` typedef
 into the definition of `Hash`, or directly by specializing `hash_is_avalanching<Hash>` to a class with
 an embedded compile-time constant `value` set to `true`.
diff --git a/include/boost/unordered/hash_traits.hpp b/include/boost/unordered/hash_traits.hpp
index 24fdf808..f6b912b7 100644
--- a/include/boost/unordered/hash_traits.hpp
+++ b/include/boost/unordered/hash_traits.hpp
@@ -53,7 +53,7 @@ struct hash_is_avalanching_impl<
  *   - Hash::is_avalanching::value if this is present and constexpr-convertible
  *     to a bool.
  *   - true if Hash::is_avalanching is void (deprecated).
- * UB otherwise.
+ *   - ill-formed otherwise.
  */
 template<typename Hash>
 struct hash_is_avalanching: detail::hash_is_avalanching_impl<Hash>::type{};