diff --git a/single/sol/sol.hpp b/single/sol/sol.hpp
index 0386872d..e808db36 100644
--- a/single/sol/sol.hpp
+++ b/single/sol/sol.hpp
@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2017-09-24 20:50:41.761192 UTC
-// This header was generated with sol v2.18.4 (revision 2eb53ac)
+// Generated 2017-09-28 23:07:20.129208 UTC
+// This header was generated with sol v2.18.4 (revision e31ed4f)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -5144,6 +5144,9 @@ namespace sol {
 	template <typename T>
 	struct is_container : detail::is_container<T> {};
 
+	template <typename T>
+	struct is_to_stringable : meta::any<meta::supports_to_string_member<meta::unqualified_t<T>>, meta::supports_adl_to_string<meta::unqualified_t<T>>, meta::supports_ostream_op<meta::unqualified_t<T>>> {};
+
 	namespace detail {
 		template <typename T, typename = void>
 		struct lua_type_of : std::integral_constant<type, type::userdata> {};
@@ -15722,7 +15725,7 @@ namespace sol {
 				usertype_detail::make_length_op<T>(l, index);
 			}
 			if (fx(meta_function::to_string)) {
-				usertype_detail::make_to_string_op<T, meta::any<meta::supports_to_string_member<T>, meta::supports_adl_to_string<T>, meta::supports_ostream_op<T>>>(l, index);
+				usertype_detail::make_to_string_op<T, is_to_stringable<T>>(l, index);
 			}
 			if (fx(meta_function::call_function)) {
 				usertype_detail::make_call_op<T>(l, index);
@@ -15750,7 +15753,7 @@ namespace sol {
 					usertype_detail::insert_default_registrations<P>(l, index, fx);
 					usertype_detail::make_destructor<T>(l, index);
 					luaL_setfuncs(L, l, 0);
-					
+
 					// __type table
 					lua_createtable(L, 0, 2);
 					const std::string& name = detail::demangle<T>();
diff --git a/sol/types.hpp b/sol/types.hpp
index 266a8da9..3ca46233 100644
--- a/sol/types.hpp
+++ b/sol/types.hpp
@@ -805,6 +805,9 @@ namespace sol {
 	template <typename T>
 	struct is_container : detail::is_container<T> {};
 
+	template <typename T>
+	struct is_to_stringable : meta::any<meta::supports_to_string_member<meta::unqualified_t<T>>, meta::supports_adl_to_string<meta::unqualified_t<T>>, meta::supports_ostream_op<meta::unqualified_t<T>>> {};
+
 	namespace detail {
 		template <typename T, typename = void>
 		struct lua_type_of : std::integral_constant<type, type::userdata> {};
diff --git a/sol/usertype_core.hpp b/sol/usertype_core.hpp
index d99dda20..d703c911 100644
--- a/sol/usertype_core.hpp
+++ b/sol/usertype_core.hpp
@@ -202,7 +202,7 @@ namespace sol {
 				usertype_detail::make_length_op<T>(l, index);
 			}
 			if (fx(meta_function::to_string)) {
-				usertype_detail::make_to_string_op<T, meta::any<meta::supports_to_string_member<T>, meta::supports_adl_to_string<T>, meta::supports_ostream_op<T>>>(l, index);
+				usertype_detail::make_to_string_op<T, is_to_stringable<T>>(l, index);
 			}
 			if (fx(meta_function::call_function)) {
 				usertype_detail::make_call_op<T>(l, index);
@@ -230,7 +230,7 @@ namespace sol {
 					usertype_detail::insert_default_registrations<P>(l, index, fx);
 					usertype_detail::make_destructor<T>(l, index);
 					luaL_setfuncs(L, l, 0);
-					
+
 					// __type table
 					lua_createtable(L, 0, 2);
 					const std::string& name = detail::demangle<T>();
diff --git a/tests/test_container_semantics.cpp b/tests/test_container_semantics.cpp
index 4ee3c32f..fa851543 100644
--- a/tests/test_container_semantics.cpp
+++ b/tests/test_container_semantics.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 #include <catch.hpp>
diff --git a/tests/test_environments.cpp b/tests/test_environments.cpp
index 04ed27a7..d617026e 100644
--- a/tests/test_environments.cpp
+++ b/tests/test_environments.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 
diff --git a/tests/test_filters.cpp b/tests/test_filters.cpp
index a4138dcb..24837adb 100644
--- a/tests/test_filters.cpp
+++ b/tests/test_filters.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 #include <catch.hpp>
diff --git a/tests/test_functions.cpp b/tests/test_functions.cpp
index 1bcaea58..f5820584 100644
--- a/tests/test_functions.cpp
+++ b/tests/test_functions.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 
diff --git a/tests/test_gc.cpp b/tests/test_gc.cpp
index 8635e472..7f6b9d0e 100644
--- a/tests/test_gc.cpp
+++ b/tests/test_gc.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 #include <catch.hpp>
diff --git a/tests/test_operators.cpp b/tests/test_operators.cpp
index 34ac7330..8ddc7dbd 100644
--- a/tests/test_operators.cpp
+++ b/tests/test_operators.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 
diff --git a/tests/test_plain_types.cpp b/tests/test_plain_types.cpp
index 0f39f42a..c6bc3711 100644
--- a/tests/test_plain_types.cpp
+++ b/tests/test_plain_types.cpp
@@ -1,4 +1,5 @@
 #define SOL_CHECK_ARGUMENTS 1
+#define SOL_ENABLE_INTEROP 1
 
 #include <sol.hpp>
 #include <catch.hpp>