diff --git a/test/boost_fusion.cpp b/test/boost_fusion.cpp
index 980a2b14..15e6d24c 100644
--- a/test/boost_fusion.cpp
+++ b/test/boost_fusion.cpp
@@ -140,11 +140,12 @@ BOOST_FUSION_ADAPT_STRUCT(
     f3  // *3
     )
 
+
+// MSVC2015's std::tuple requires default constructor during 'as' process.
+// It doesn't support Expression SFINAE yet, then 'as' is fallbacked to 'convert'.
+// After MSVC would support Expression SFINAE, remove this guard.
 #if !defined(_MSC_VER)
 
-// boost::fusion's adaptor uses std::tuple.
-// MSVC2015's std::tuple requires default constructor during 'as' process.
-// I don't know why...
 TEST(MSGPACK_BOOST, pack_convert_no_def_con)
 {
     std::stringstream ss;
diff --git a/test/msgpack_cpp11.cpp b/test/msgpack_cpp11.cpp
index b1686a31..b5b8b523 100644
--- a/test/msgpack_cpp11.cpp
+++ b/test/msgpack_cpp11.cpp
@@ -456,10 +456,13 @@ TEST(MSGPACK_NO_DEF_CON_PAIR, simple_buffer)
     EXPECT_EQ(val1, val2);
 }
 
-#if !defined(_MSC_VER)
+
 
 // MSVC2015's std::tuple requires default constructor during 'as' process.
-// I don't know why...
+// It doesn't support Expression SFINAE yet, then 'as' is fallbacked to 'convert'.
+// After MSVC would support Expression SFINAE, remove this guard.
+#if !defined(_MSC_VER)
+
 TEST(MSGPACK_NO_DEF_CON_TUPLE, simple_buffer)
 {
     std::tuple<no_def_con, no_def_con, no_def_con_composite> val1 {1, 2, 3};