diff --git a/include/boost/multi/detail/layout.hpp b/include/boost/multi/detail/layout.hpp
index bf5de5d7d..134aa4eb1 100644
--- a/include/boost/multi/detail/layout.hpp
+++ b/include/boost/multi/detail/layout.hpp
@@ -157,7 +157,8 @@ struct extensions_t : boost::multi::detail::tuple_prepend_t<index_extension, typ
 	constexpr extensions_t(index_extension const& extension, typename layout_t<D-1>::extensions_type const& other)
 	: extensions_t(multi::detail::ht_tuple(extension, other.base())) {}
 
-	constexpr auto base()            const&    -> base_ const& {return *this;} // impl_;}
+	constexpr auto base()            const&    -> base_ const& { return *this; } // impl_;}
+	constexpr auto base()                 &    -> base_      & { return *this; } // impl_;}
 
 	friend constexpr auto operator*(index_extension const& extension, extensions_t const& self) -> extensions_t<D + 1> {
 		// return extensions_t<D + 1>(tuple(extension, self.base()));
@@ -292,7 +293,8 @@ template<> struct extensions_t<0> : tuple<> {
 
 	extensions_t() = default;
 
-	constexpr auto base() const -> base_ const& {return *this;}
+	constexpr auto base() const& -> base_ const& { return *this; }
+	constexpr auto base()      & -> base_      & { return *this; }
 
 	template<class Archive> static void serialize(Archive&/*ar*/, unsigned /*version*/) {/*noop*/}
 
@@ -353,7 +355,9 @@ template<> struct extensions_t<1> : tuple<multi::index_extension> {
 	constexpr explicit extensions_t(base_ tup) : base_{tup} {}
 
 	extensions_t() = default;
-	constexpr auto base() const -> base_ const& {return *this;}
+
+	constexpr auto base() const& -> base_ const& { return *this; }
+	constexpr auto base()      & -> base_      & { return *this; }
 
 	BOOST_MULTI_HD constexpr auto operator==(extensions_t const& other) const -> bool {return base() == other.base();}  // when compiling as cuda code, this needs --expt-relaxed-constexpr
 	BOOST_MULTI_HD constexpr auto operator!=(extensions_t const& other) const -> bool {return base() != other.base();}
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index d019eb5d5..a3f38ed38 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -24,6 +24,7 @@ else()
 	option(CMAKE_COMPILE_WARNING_AS_ERROR "Compile warnings as errors" ON)
 
 	find_package(Boost CONFIG)
+	find_package(Boost COMPONENTS serialization)
 
 	if(ENABLE_CUDA)
 		enable_language(CUDA)
@@ -383,7 +384,7 @@ else()
 			add_test(NAME ${TEST_EXE} COMMAND $<TARGET_FILE:${TEST_EXE}>)
 		endforeach()
 
-		target_link_libraries    (${TEST_EXE} PRIVATE TBB::tbb)
+		# target_link_libraries    (serialization.cpp.x PRIVATE Boost::serialization)
 
 	endif()
 endif()