diff --git a/README.md b/README.md
index 077a2f0..56c3f3f 100644
--- a/README.md
+++ b/README.md
@@ -1455,9 +1455,77 @@ There are some unreleased features in toml-lang/toml:master.
 Currently, the following features are available after defining
 `TOML11_USE_UNRELEASED_TOML_FEATURES` macro flag.
 
+To use those features, `#define` `TOML11_USE_UNRELEASED_TOML_FEATURES` before
+including `toml.hpp` or pass `-DTOML11_USE_UNRELEASED_TOML_FEATURES` to your
+compiler.
+
 - Leading zeroes in exponent parts of floats are permitted.
   - e.g. `1.0e+01`, `5e+05`
+  - [toml-lang/toml/PR/656](https://github.com/toml-lang/toml/pull/656)
 - Allow raw tab characters in basic strings and multi-line basic strings.
+  - [toml-lang/toml/PR/627](https://github.com/toml-lang/toml/pull/627)
+- Allow heterogeneous arrays
+  - [toml-lang/toml/PR/676](https://github.com/toml-lang/toml/pull/676)
+
+### Note about heterogeneous arrays
+
+Although `toml::parse` allows heterogeneous arrays, constructor of `toml::value`
+does not.
+
+```cpp
+// this won't be compiled
+toml::value v{
+    "foo", 3.14, 42, {1,2,3,4,5}, {{"key", "value"}}
+}
+```
+
+There is a workaround for this issue. By explicitly converting values into
+`toml::value`, you can initialize `toml::value` with a heterogeneous array.
+
+```cpp
+// OK!
+toml::value v{
+    toml::value("foo"), toml::value(3.14), toml::value(42),
+    toml::value{1,2,3,4,5}, toml::value{{"key", "value"}}
+}
+```
+
+The reason why the first example is not allowed is the following.
+Let's assume that you are initializing a `toml::value` with a table.
+
+```cpp
+                    // # expecting TOML table.
+toml::value v{      // [v]
+    {"answer", 42}, // answer = 42
+    {"pi",   3.14}, // pi = 3.14
+    {"foo", "bar"}  // foo = "bar"
+};
+```
+
+This is indistinguishable from a (heterogeneous) TOML array definition.
+
+```toml
+v = [
+    ["answer", 42],
+    ["pi",   3.14],
+    ["foo", "bar"],
+]
+```
+
+This means that the above C++ code makes constructor's overload resolution
+ambiguous. So a constructor that allows both "table as an initializer-list" and
+"heterogeneous array as an initializer-list" cannot be implemented.
+
+Thus, although it is painful, you need to explicitly cast values into
+`toml::value` when you initialize heterogeneous array in C++ code.
+
+```cpp
+// You need to do this when you want to initialize hetero array.
+toml::value v{
+    toml::value("foo"), toml::value(3.14), toml::value(42),
+    toml::value{1,2,3,4,5}, toml::value{{"key", "value"}}
+}
+```
 
 ## Breaking Changes from v2
 
diff --git a/tests/test_error_detection.cpp b/tests/test_error_detection.cpp
index c936209..49dff6e 100644
--- a/tests/test_error_detection.cpp
+++ b/tests/test_error_detection.cpp
@@ -80,10 +80,14 @@ BOOST_AUTO_TEST_CASE(test_detect_conflicting_value)
 
 BOOST_AUTO_TEST_CASE(test_detect_inhomogeneous_array)
 {
+#ifdef TOML11_USE_UNRELEASED_TOML_FEATURES
+    BOOST_TEST_MESSAGE("heterogeneous array will be allowed in the next release");
+#else
     std::istringstream stream(std::string(
             "a = [1, 1.0]\n"
             ));
     BOOST_CHECK_THROW(toml::parse(stream), toml::syntax_error);
+#endif
 }
 
 BOOST_AUTO_TEST_CASE(test_detect_appending_array_of_table)
diff --git a/tests/test_parse_array.cpp b/tests/test_parse_array.cpp
index 9cfbc4d..2dafdb9 100644
--- a/tests/test_parse_array.cpp
+++ b/tests/test_parse_array.cpp
@@ -128,3 +128,47 @@ BOOST_AUTO_TEST_CASE(test_multiline_array_value)
         TOML11_TEST_PARSE_EQUAL_VALUE(parse_value<toml::value>, "[\"foo\",#comment\n\"b#r\",#comment\n\"b#z\"#comment\n]", toml::value(a));
     }
 }
+
+BOOST_AUTO_TEST_CASE(test_heterogeneous_array)
+{
+#ifndef TOML11_USE_UNRELEASED_TOML_FEATURES
+    BOOST_TEST_MESSAGE("In strict TOML v0.5.0, heterogeneous arrays are not allowed.");
+#else
+    {
+        array a(5);
+        a[0] = toml::value("foo");
+        a[1] = toml::value(3.14);
+        a[2] = toml::value(42);
+        a[3] = toml::value{toml::value("array"), toml::value("of"), toml::value("hetero-array"), toml::value(1)};
+        a[4] = toml::value{{"key", "value"}};
+        TOML11_TEST_PARSE_EQUAL_VALUE(parse_value<toml::value>, "[\"foo\", 3.14, 42, [\"array\", \"of\", \"hetero-array\", 1], {key = \"value\"}]", toml::value(a));
+    }
+    {
+        array a(5);
+        a[0] = toml::value("foo");
+        a[1] = toml::value(3.14);
+        a[2] = toml::value(42);
+        a[3] = toml::value{toml::value("array"), toml::value("of"), toml::value("hetero-array"), toml::value(1)};
+        a[4] = toml::value{{"key", "value"}};
+        TOML11_TEST_PARSE_EQUAL_VALUE(parse_value<toml::value>, "[\"foo\",\n 3.14,\n 42,\n [\"array\", \"of\", \"hetero-array\", 1],\n {key = \"value\"},\n]", toml::value(a));
+    }
+    {
+        array a(5);
+        a[0] = toml::value("foo");
+        a[1] = toml::value(3.14);
+        a[2] = toml::value(42);
+        a[3] = toml::value{toml::value("array"), toml::value("of"), toml::value("hetero-array"), toml::value(1)};
+        a[4] = toml::value{{"key", "value"}};
+        TOML11_TEST_PARSE_EQUAL_VALUE(parse_value<toml::value>, "[\"foo\",#comment\n 3.14,#comment\n 42,#comment\n [\"array\", \"of\", \"hetero-array\", 1],#comment\n {key = \"value\"},#comment\n]#comment", toml::value(a));
+    }
+    {
+        array a(5);
+        a[0] = toml::value("foo");
+        a[1] = toml::value(3.14);
+        a[2] = toml::value(42);
+        a[3] = toml::value{toml::value("array"), toml::value("of"), toml::value("hetero-array"), toml::value(1)};
+        a[4] = toml::value{{"key", "value"}};
+        TOML11_TEST_PARSE_EQUAL_VALUE(parse_value<toml::value>, "[\"foo\",\n 3.14,\n 42,\n [\"array\",\n \"of\",\n \"hetero-array\",\n 1],\n {key = \"value\"},\n]", toml::value(a));
+    }
+#endif
+}
diff --git a/toml/parser.hpp b/toml/parser.hpp
index 9fd7097..0efccf0 100644
--- a/toml/parser.hpp
+++ b/toml/parser.hpp
@@ -938,6 +938,7 @@ parse_array(location<Container>& loc)
 
         if(auto val = parse_value<value_type>(loc))
         {
+#ifndef TOML11_USE_UNRELEASED_TOML_FEATURES
             if(!retval.empty() && retval.front().type() != val.as_ok().type())
             {
                 auto array_start_loc = loc;
@@ -956,6 +957,7 @@ parse_array(location<Container>& loc)
                         }
                     }), source_location(std::addressof(loc)));
             }
+#endif
             retval.push_back(std::move(val.unwrap()));
         }
         else