diff --git a/include/boost/http_proto/detail/impl/workspace.hpp b/include/boost/http_proto/detail/impl/workspace.hpp
index 74aa72c7..04d38b1d 100644
--- a/include/boost/http_proto/detail/impl/workspace.hpp
+++ b/include/boost/http_proto/detail/impl/workspace.hpp
@@ -36,11 +36,12 @@ struct alignas(alignof(::max_align_t))
     U u;
 
     any_impl() = delete;
-    any_impl(any_impl&&) = default;
+    any_impl(any_impl const&) = delete;
+    any_impl(any_impl&&) = delete;
 
-    template<class U_>
-    explicit any_impl(U_&& u_)
-        : u(std::move(u_))
+    template<class... Args>
+    explicit any_impl(Args&&... args)
+        : u(std::forward<Args>(args)...)
     {
     }
 };
@@ -86,10 +87,10 @@ space_needed()
     return sizeof(any_impl<U>);
 }
 
-template<class T>
+template<class T, class... Args>
 auto
 workspace::
-push(T&& t) ->
+emplace(Args&&... args) ->
     typename std::decay<T>::type&
 {
     static_assert(
@@ -102,7 +103,7 @@ push(T&& t) ->
     undo u(*this);
     auto p = ::new(bump_down(
         sizeof(U), alignof(U))) U(
-            std::forward<T>(t));
+            std::forward<Args>(args)...);
     u.commit();
     p->next = reinterpret_cast<
         any*>(head_);
@@ -111,6 +112,15 @@ push(T&& t) ->
     return p->u;
 }
 
+template<class T>
+auto
+workspace::
+push(T&& t) ->
+    typename std::decay<T>::type&
+{
+    return emplace<T>(std::forward<T>(t));
+}
+
 template<class T>
 T*
 workspace::
diff --git a/include/boost/http_proto/detail/workspace.hpp b/include/boost/http_proto/detail/workspace.hpp
index 81b9fba1..33df366f 100644
--- a/include/boost/http_proto/detail/workspace.hpp
+++ b/include/boost/http_proto/detail/workspace.hpp
@@ -128,6 +128,10 @@ class workspace
     reserve_front(
         std::size_t n);
 
+    template<class T, class... Args>
+    typename std::decay<T>::type&
+    emplace(Args&&... args);
+
     template<class T>
     typename std::decay<T>::type&
     push(T&& t);
diff --git a/include/boost/http_proto/impl/serializer.hpp b/include/boost/http_proto/impl/serializer.hpp
index d49d69e3..10068be5 100644
--- a/include/boost/http_proto/impl/serializer.hpp
+++ b/include/boost/http_proto/impl/serializer.hpp
@@ -12,8 +12,6 @@
 
 #include <boost/http_proto/detail/except.hpp>
 #include <boost/buffers/range.hpp>
-#include <iterator>
-#include <new>
 #include <utility>
 
 namespace boost {
@@ -91,21 +89,23 @@ start(
 
 template<
     class Source,
+    class... Args,
     class>
-auto
+Source&
 serializer::
 start(
     message_view_base const& m,
-    Source&& src0) ->
-        typename std::decay<
-            Source>::type&
+    Args&&... args)
 {
+    static_assert(
+        std::is_constructible<Source, Args...>::value ||
+        std::is_constructible<Source, buffered_base::allocator&, Args...>::value,
+        "The Source cannot be constructed with the given arguments");
+
     start_init(m);
-    auto& src = ws_.push(
-        std::forward<
-            Source>(src0));
-    start_source(
-        m, std::addressof(src));
+    auto& src = construct_source<Source>(
+        std::forward<Args>(args)...);
+    start_source(m, std::addressof(src));
     return src;
 }
 
diff --git a/include/boost/http_proto/serializer.hpp b/include/boost/http_proto/serializer.hpp
index 5d4b643d..2c19c75a 100644
--- a/include/boost/http_proto/serializer.hpp
+++ b/include/boost/http_proto/serializer.hpp
@@ -130,18 +130,17 @@ class BOOST_SYMBOL_VISIBLE
         undefined behavior.
     */
     template<
-        class Source
+        class Source,
+        class... Args
 #ifndef BOOST_HTTP_PROTO_DOCS
         ,class = typename std::enable_if<
             is_source<Source>::value>::type
 #endif
     >
-    auto
+    Source&
     start(
         message_view_base const& m,
-        Source&& body) ->
-            typename std::decay<
-                Source>::type&;
+        Args&&... args);
 
     //--------------------------------------------
 
@@ -192,6 +191,41 @@ class BOOST_SYMBOL_VISIBLE
     make_array(std::size_t n) ->
         detail::array_of_const_buffers;
 
+    template<
+        class Source,
+        class... Args,
+        typename std::enable_if<
+            std::is_constructible<
+                Source,
+                Args...>::value>::type* = nullptr>
+    Source&
+    construct_source(Args&&... args)
+    {
+        return ws_.emplace<Source>(
+            std::forward<Args>(args)...);
+    }
+
+    template<
+        class Source,
+        class... Args,
+        typename std::enable_if<
+            std::is_constructible<
+                Source,
+                buffered_base::allocator&,
+                Args...>::value>::type* = nullptr>
+    Source&
+    construct_source(Args&&... args)
+    {
+        buffered_base::allocator a(
+            ws_.data(),
+            (ws_.size() - ws_.space_needed<Source>()) / 2,
+            false);
+        auto& src = ws_.emplace<Source>(
+            a, std::forward<Args>(args)...);
+        ws_.reserve_front(a.size_used());
+        return src;
+    }
+
     BOOST_HTTP_PROTO_DECL void start_init(message_view_base const&);
     BOOST_HTTP_PROTO_DECL void start_empty(message_view_base const&);
     BOOST_HTTP_PROTO_DECL void start_buffers(message_view_base const&);
diff --git a/include/boost/http_proto/source.hpp b/include/boost/http_proto/source.hpp
index ff086df4..62d2b5f9 100644
--- a/include/boost/http_proto/source.hpp
+++ b/include/boost/http_proto/source.hpp
@@ -34,7 +34,6 @@ namespace http_proto {
 */
 struct BOOST_HTTP_PROTO_DECL
     source
-    : buffered_base
 {
     /** The results of producing data.
     */
diff --git a/src/serializer.cpp b/src/serializer.cpp
index 65b00831..70305744 100644
--- a/src/serializer.cpp
+++ b/src/serializer.cpp
@@ -435,11 +435,6 @@ start_source(
         2); // tmp
     //if(! cod_)
     {
-        buffered_base::allocator a(
-            ws_.data(), ws_.size()/2, false);
-        src->init(a);
-        ws_.reserve_front(a.size_used());
-
         tmp0_ = { ws_.data(), ws_.size() };
         if(tmp0_.capacity() <
                 18 +    // chunk size
diff --git a/test/unit/serializer.cpp b/test/unit/serializer.cpp
index 55d58799..8ff5dfc2 100644
--- a/test/unit/serializer.cpp
+++ b/test/unit/serializer.cpp
@@ -40,7 +40,7 @@ struct serializer_test
 
         results
         on_read(
-            buffers::mutable_buffer b)
+            buffers::mutable_buffer b) override
         {
             BOOST_TEST(! is_done_);
             results rv;
@@ -162,10 +162,10 @@ struct serializer_test
         sr.start(res);
         sr.start(res, buffers::const_buffer{});
         sr.start(res, buffers::mutable_buffer{});
-        sr.start(res, test_source{"12345"});
+        sr.start<test_source>(res, "12345");
         sr.start(res, make_const(buffers::const_buffer{}));
         sr.start(res, make_const(buffers::mutable_buffer{}));
-        sr.start(res, make_const(test_source{"12345"}));
+        sr.start<test_source>(res, make_const("12345"));
 
         serializer(65536);
 #ifdef BOOST_HTTP_PROTO_HAS_ZLIB
@@ -244,7 +244,7 @@ struct serializer_test
         // we limit the buffer size of the serializer, requiring
         // it to make multiple calls to source::read
         serializer sr(1024);
-        sr.start(res, std::forward<
+        sr.start<Source>(res, std::forward<
             Source>(src));
         std::string s = read(sr);
         f(s);
@@ -377,7 +377,7 @@ struct serializer_test
                 "Expect: 100-continue\r\n"
                 "Content-Length: 5\r\n"
                 "\r\n");
-            sr.start(req, test_source{"12345"});
+            sr.start<test_source>(req, "12345");
             std::string s;
             system::result<
                 serializer::const_buffers_type> rv;
@@ -457,7 +457,7 @@ struct serializer_test
                 "\r\n";
             serializer sr;
             response res(sv);
-            sr.start(res, test_source{"12345"});
+            sr.start<test_source>(res, "12345");
             auto s = read(sr);
             BOOST_TEST(s ==
                 "HTTP/1.1 200 OK\r\n"