diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71d3dae5..3a786148 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 Version 205
 
 * Doc work
+* Add detail/soft_mutex.hpp
 
 --------------------------------------------------------------------------------
 
diff --git a/include/boost/beast/websocket/detail/soft_mutex.hpp b/include/boost/beast/websocket/detail/soft_mutex.hpp
new file mode 100644
index 00000000..8fe7a0b2
--- /dev/null
+++ b/include/boost/beast/websocket/detail/soft_mutex.hpp
@@ -0,0 +1,112 @@
+//
+// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+#ifndef BOOST_BEAST_WEBSOCKET_DETAIL_SOFT_MUTEX_HPP
+#define BOOST_BEAST_WEBSOCKET_DETAIL_SOFT_MUTEX_HPP
+
+#include <boost/assert.hpp>
+
+namespace boost {
+namespace beast {
+namespace websocket {
+namespace detail {
+
+// used to order reads, writes in websocket streams
+
+class soft_mutex
+{
+    int id_ = 0;
+
+public:
+    soft_mutex() = default;
+    soft_mutex(soft_mutex const&) = delete;
+    soft_mutex& operator=(soft_mutex const&) = delete;
+
+    soft_mutex(soft_mutex&& other) noexcept
+        : id_(boost::exchange(other.id_, 0))
+    {
+    }
+
+    soft_mutex& operator=(soft_mutex&& other) noexcept
+    {
+        id_ = other.id_;
+        other.id_ = 0;
+        return *this;
+    }
+
+    // VFALCO I'm not too happy that this function is needed
+    void
+    reset()
+    {
+        id_ = 0;
+    }
+
+    bool
+    is_locked() const noexcept
+    {
+        return id_ != 0;
+    }
+
+    template<class T>
+    bool
+    is_locked(T const*) const noexcept
+    {
+        return id_ == T::id;
+    }
+
+    template<class T>
+    void
+    lock(T const*)
+    {
+        BOOST_ASSERT(id_ == 0);
+        id_ = T::id;
+    }
+
+    template<class T>
+    void
+    unlock(T const*)
+    {
+        BOOST_ASSERT(id_ == T::id);
+        id_ = 0;
+    }
+
+    template<class T>
+    bool
+    try_lock(T const*)
+    {
+        // If this assert goes off it means you are attempting to
+        // simultaneously initiate more than one of same asynchronous
+        // operation, which is not allowed. For example, you must wait
+        // for an async_read to complete before performing another
+        // async_read.
+        //
+        BOOST_ASSERT(id_ != T::id);
+        if(id_ != 0)
+            return false;
+        id_ = T::id;
+        return true;
+    }
+
+    template<class T>
+    bool
+    try_unlock(T const*) noexcept
+    {
+        if(id_ != T::id)
+            return false;
+        id_ = 0;
+        return true;
+    }
+};
+
+} // detail
+} // websocket
+} // beast
+} // boost
+
+#endif
diff --git a/include/boost/beast/websocket/detail/stream_base.hpp b/include/boost/beast/websocket/detail/stream_base.hpp
index b029e76d..95237731 100644
--- a/include/boost/beast/websocket/detail/stream_base.hpp
+++ b/include/boost/beast/websocket/detail/stream_base.hpp
@@ -7,8 +7,8 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
-#ifndef BOOST_BEAST_WEBSOCKET_STREAM_BASE_HPP
-#define BOOST_BEAST_WEBSOCKET_STREAM_BASE_HPP
+#ifndef BOOST_BEAST_WEBSOCKET_DETAIL_STREAM_BASE_HPP
+#define BOOST_BEAST_WEBSOCKET_DETAIL_STREAM_BASE_HPP
 
 #include <boost/beast/http/empty_body.hpp>
 #include <boost/beast/http/message.hpp>
@@ -43,87 +43,6 @@ namespace beast {
 namespace websocket {
 namespace detail {
 
-// used to order reads and writes
-class soft_mutex
-{
-    int id_ = 0;
-
-public:
-    soft_mutex() = default;
-    soft_mutex(soft_mutex const&) = delete;
-    soft_mutex& operator=(soft_mutex const&) = delete;
-
-    soft_mutex(soft_mutex&& other) noexcept
-        : id_(boost::exchange(other.id_, 0))
-    {
-    }
-
-    soft_mutex& operator=(soft_mutex&& other) noexcept
-    {
-        id_ = other.id_;
-        other.id_ = 0;
-        return *this;
-    }
-
-    // VFALCO I'm not too happy that this function is needed
-    void reset()
-    {
-        id_ = 0;
-    }
-
-    bool is_locked() const
-    {
-        return id_ != 0;
-    }
-
-    template<class T>
-    bool is_locked(T const*) const
-    {
-        return id_ == T::id;
-    }
-
-    template<class T>
-    void lock(T const*)
-    {
-        BOOST_ASSERT(id_ == 0);
-        id_ = T::id;
-    }
-
-    template<class T>
-    void unlock(T const*)
-    {
-        BOOST_ASSERT(id_ == T::id);
-        id_ = 0;
-    }
-
-    template<class T>
-    bool try_lock(T const*)
-    {
-        // If this assert goes off it means you are attempting to
-        // simultaneously initiate more than one of same asynchronous
-        // operation, which is not allowed. For example, you must wait
-        // for an async_read to complete before performing another
-        // async_read.
-        //
-        BOOST_ASSERT(id_ != T::id);
-        if(id_ != 0)
-            return false;
-        id_ = T::id;
-        return true;
-    }
-
-    template<class T>
-    bool try_unlock(T const*)
-    {
-        if(id_ != T::id)
-            return false;
-        id_ = 0;
-        return true;
-    }
-};
-
-//------------------------------------------------------------------------------
-
 struct stream_prng
 {
     bool secure_prng_ = true;
diff --git a/include/boost/beast/websocket/stream.hpp b/include/boost/beast/websocket/stream.hpp
index 7b73a636..beca0e96 100644
--- a/include/boost/beast/websocket/stream.hpp
+++ b/include/boost/beast/websocket/stream.hpp
@@ -20,6 +20,7 @@
 #include <boost/beast/websocket/detail/hybi13.hpp>
 #include <boost/beast/websocket/detail/mask.hpp>
 #include <boost/beast/websocket/detail/pmd_extension.hpp>
+#include <boost/beast/websocket/detail/soft_mutex.hpp>
 #include <boost/beast/websocket/detail/stream_base.hpp>
 #include <boost/beast/websocket/detail/utf8_checker.hpp>
 #include <boost/beast/core/saved_handler.hpp>