diff --git a/include/nanorange/detail/ranges/concepts.hpp b/include/nanorange/detail/ranges/concepts.hpp
index a188533..62068c1 100644
--- a/include/nanorange/detail/ranges/concepts.hpp
+++ b/include/nanorange/detail/ranges/concepts.hpp
@@ -14,26 +14,7 @@
 #include <nanorange/detail/ranges/range_concept.hpp>
 
 #include <initializer_list>
-
-// Avoid dragging in the large <set> and <unordered_set> headers
-// This is technically undefined behaviour: define the symbol
-// NANORANGE_NO_STD_FORWARD_DECLARATIONS
-// to enforce standard-compliant mode
-#ifndef NANORANGE_NO_STD_FORWARD_DECLARATIONS
-NANO_BEGIN_NAMESPACE_STD
-template <typename, typename> class basic_string_view;
-template <typename, typename, typename> class set;
-template <typename, typename, typename> class multiset;
-template <typename, typename, typename, typename> class unordered_set;
-template <typename, typename, typename, typename> class unordered_multiset;
-template <typename, typename> class match_results;
-NANO_END_NAMESPACE_STD
-#else
 #include <string_view>
-#include <regex>
-#include <set>
-#include <unordered_set>
-#endif
 
 NANO_BEGIN_NAMESPACE
 
@@ -67,47 +48,12 @@ NANO_CONCEPT sized_range =
 // [range.views]
 struct view_base { };
 
-namespace detail {
-
-template <typename>
-inline constexpr bool is_std_non_view = false;
-
-template <typename T>
-inline constexpr bool is_std_non_view<std::initializer_list<T>> = true;
-
-template <typename K, typename C, typename A>
-inline constexpr bool is_std_non_view<std::set<K, C, A>> = true;
-
-template <typename K, typename C, typename A>
-inline constexpr bool is_std_non_view<std::multiset<K, C, A>> = true;
-
-template <typename K, typename H, typename E, typename A>
-inline constexpr bool is_std_non_view<std::unordered_set<K, H, E, A>> = true;
-
-template <typename K, typename H, typename E, typename A>
-inline constexpr bool is_std_non_view<std::unordered_multiset<K, H, E, A>> = true;
-
-template <typename B, typename A>
-inline constexpr bool is_std_non_view<std::match_results<B, A>> = true;
-
 template <typename T>
-constexpr bool enable_view_helper()
-{
-    if constexpr (derived_from<T, view_base>) {
-        return true;
-    } else if constexpr (is_std_non_view<T>) {
-        return false;
-    } else if constexpr (range<T> && range<const T>) {
-        return same_as<range_reference_t<T>, range_reference_t<const T>>;
-    } else {
-        return true;
-    }
-}
+inline constexpr bool enable_view = derived_from<T, view_base>;
 
-}
-
-template <typename T>
-inline constexpr bool enable_view = detail::enable_view_helper<T>();
+// Special-case std::string_view
+template <typename CharT, typename Traits>
+inline constexpr bool enable_view<std::basic_string_view<CharT, Traits>> = true;
 
 template <typename T>
 NANO_CONCEPT view = range<T> && semiregular<T> && enable_view<T>;
diff --git a/include/nanorange/views/empty.hpp b/include/nanorange/views/empty.hpp
index 2d41792..a58349c 100644
--- a/include/nanorange/views/empty.hpp
+++ b/include/nanorange/views/empty.hpp
@@ -14,19 +14,15 @@ NANO_BEGIN_NAMESPACE
 namespace empty_view_ {
 
 template <typename T>
-class empty_view : view_interface<empty_view<T>> {
-    static_assert(std::is_object<T>::value, "");
+class empty_view : public view_interface<empty_view<T>> {
+    static_assert(std::is_object<T>::value);
 
 public:
     static constexpr T* begin() noexcept { return nullptr; }
     static constexpr T* end() noexcept { return nullptr; }
-    static constexpr std::ptrdiff_t size() noexcept { return 0; }
+    static constexpr std::size_t size() noexcept { return 0; }
     static constexpr T* data() noexcept { return nullptr; }
-
     static constexpr bool empty() noexcept { return true; }
-
-    friend constexpr T* begin(empty_view) noexcept { return nullptr; }
-    friend constexpr T* end(empty_view) noexcept { return nullptr; }
 };
 
 }
diff --git a/include/nanorange/views/split.hpp b/include/nanorange/views/split.hpp
index 433efeb..22ece2a 100644
--- a/include/nanorange/views/split.hpp
+++ b/include/nanorange/views/split.hpp
@@ -116,7 +116,7 @@ struct split_view : view_interface<split_view<V, Pattern>> {
         using iterator_category = detail::conditional_t<
             forward_range<Base>, forward_iterator_tag, input_iterator_tag>;
 
-        struct value_type {
+        struct value_type : view_interface<value_type> {
         private:
             outer_iterator i_ = outer_iterator();
 
diff --git a/test/concepts/ranges.cpp b/test/concepts/ranges.cpp
index 00a49bd..e42dfc8 100644
--- a/test/concepts/ranges.cpp
+++ b/test/concepts/ranges.cpp
@@ -170,7 +170,7 @@ void ridiculously_exhaustive_range_property_test() {
 	// FIXME: This no longer asserts with P0970. Is that intentional?
 //	CONCEPT_ASSERT(!models::SizedRange<mutable_only_unsized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<mutable_only_unsized_range>);
-	CONCEPT_ASSERT(models::view<mutable_only_unsized_range>);
+	//CONCEPT_ASSERT(models::view<mutable_only_unsized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<mutable_only_unsized_range&>, I>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<mutable_only_unsized_range&>, I>);
@@ -196,7 +196,7 @@ void ridiculously_exhaustive_range_property_test() {
 	CONCEPT_ASSERT(models::range<immutable_unsized_range>);
 	CONCEPT_ASSERT(models::sized_range<immutable_unsized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<immutable_unsized_range>);
-	CONCEPT_ASSERT(models::view<immutable_unsized_range>);
+	//CONCEPT_ASSERT(models::view<immutable_unsized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<immutable_unsized_range&>, CI>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<immutable_unsized_range&>, CI>);
@@ -254,7 +254,7 @@ void ridiculously_exhaustive_range_property_test() {
 	CONCEPT_ASSERT(models::range<mutable_only_sized_range>);
 	CONCEPT_ASSERT(models::sized_range<mutable_only_sized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<mutable_only_sized_range>);
-	CONCEPT_ASSERT(models::view<mutable_only_sized_range>);
+	//CONCEPT_ASSERT(models::view<mutable_only_sized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<mutable_only_sized_range&>, I>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<mutable_only_sized_range&>, I>);
@@ -279,7 +279,7 @@ void ridiculously_exhaustive_range_property_test() {
 	CONCEPT_ASSERT(models::range<immutable_sized_range>);
 	CONCEPT_ASSERT(models::sized_range<immutable_sized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<immutable_sized_range>);
-	CONCEPT_ASSERT(models::view<immutable_sized_range>);
+	//CONCEPT_ASSERT(models::view<immutable_sized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<immutable_sized_range&>, CI>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<immutable_sized_range&>, CI>);
@@ -337,7 +337,7 @@ void ridiculously_exhaustive_range_property_test() {
 	CONCEPT_ASSERT(models::range<mutable_only_badsized_range>);
 	CONCEPT_ASSERT(!models::sized_range<mutable_only_badsized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<mutable_only_badsized_range>);
-	CONCEPT_ASSERT(models::view<mutable_only_badsized_range>);
+	//CONCEPT_ASSERT(models::view<mutable_only_badsized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<mutable_only_badsized_range&>, I>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<mutable_only_badsized_range&>, I>);
@@ -362,7 +362,7 @@ void ridiculously_exhaustive_range_property_test() {
 	CONCEPT_ASSERT(models::range<immutable_badsized_range>);
 	CONCEPT_ASSERT(!models::sized_range<immutable_badsized_range>);
 	//CONCEPT_ASSERT(!models::_ContainerLike<immutable_badsized_range>);
-	CONCEPT_ASSERT(models::view<immutable_badsized_range>);
+	//CONCEPT_ASSERT(models::view<immutable_badsized_range>);
 
 	CONCEPT_ASSERT(models::same_as<ns::iterator_t<immutable_badsized_range&>, CI>);
 	CONCEPT_ASSERT(models::same_as<ns::sentinel_t<immutable_badsized_range&>, CI>);
@@ -414,7 +414,7 @@ void ridiculously_exhaustive_range_property_test() {
 
 	CONCEPT_ASSERT(models::range<mutable_only_unsized_range&>);
 	CONCEPT_ASSERT(models::range<mutable_only_unsized_range>);
-	CONCEPT_ASSERT(models::view<mutable_only_unsized_range>);
+	//CONCEPT_ASSERT(models::view<mutable_only_unsized_range>);
 	CONCEPT_ASSERT(!models::view<mutable_only_unsized_range&>);
 	CONCEPT_ASSERT(!models::view<mutable_only_unsized_range&&>);
 	CONCEPT_ASSERT(!models::range<const mutable_only_unsized_range&>);
@@ -442,7 +442,7 @@ ns::iterator_t<R> complicated_algorithm(R&& r) {
 }
 
 template <class T>
-struct array_view {
+struct array_view : nano::view_base {
 	T* first_;
 	std::size_t n_;
 
diff --git a/test/utility/concepts.cpp b/test/utility/concepts.cpp
index 7647387..483e79c 100644
--- a/test/utility/concepts.cpp
+++ b/test/utility/concepts.cpp
@@ -267,7 +267,7 @@ static_assert(
         ranges::concepts::View
     >::value, "");*/
 
-struct myview {
+struct myview : ranges::view_base {
     const char *begin();
     const char *end();
 };