diff --git a/types/traits.hpp b/types/traits.hpp
index 07eb0fdf..e407af52 100644
--- a/types/traits.hpp
+++ b/types/traits.hpp
@@ -349,28 +349,30 @@ template <typename T>
 constexpr auto is_contiguous_v = is_contiguous<T>::value;
 
 
-///////////////////////////////////////////////////////////////////////////////
-/// stores the type of '::value_type' for a given type, or the type itself if
-/// it does not have such a type.
-template <typename ValueT, typename = std::void_t<>>
-struct inner_type {
-    using type = ValueT;
-};
+namespace util {
+    ///////////////////////////////////////////////////////////////////////////////
+    /// stores the type of '::value_type' for a given type, or the type itself if
+    /// it does not have such a type.
+    template <typename ValueT, typename = std::void_t<>>
+    struct inner_type {
+        using type = ValueT;
+    };
 
 
-//-----------------------------------------------------------------------------
-template <typename ValueT>
-struct inner_type<
-    ValueT,
-    std::void_t<typename ValueT::value_type>
-> {
-    using type = typename ValueT::value_type;
-};
+    //-----------------------------------------------------------------------------
+    template <typename ValueT>
+    struct inner_type<
+        ValueT,
+        std::void_t<typename ValueT::value_type>
+    > {
+        using type = typename ValueT::value_type;
+    };
 
 
-//-----------------------------------------------------------------------------
-template <typename ValueT>
-using inner_type_t = typename inner_type<ValueT>::type;
+    //-----------------------------------------------------------------------------
+    template <typename ValueT>
+    using inner_type_t = typename inner_type<ValueT>::type;
+}
 
 
 ///////////////////////////////////////////////////////////////////////////////