diff --git a/include/boost/coroutine/detail/symmetric_coroutine_impl.hpp b/include/boost/coroutine/detail/symmetric_coroutine_impl.hpp
index 7d52d04..916a48b 100644
--- a/include/boost/coroutine/detail/symmetric_coroutine_impl.hpp
+++ b/include/boost/coroutine/detail/symmetric_coroutine_impl.hpp
@@ -145,22 +145,22 @@ public:
     }
 
     template< typename X >
-    R * yield_to( symmetric_coroutine_impl< X > * other, X x)
+    R * yield_to( symmetric_coroutine_impl< X > * other, X const& x)
     {
         BOOST_ASSERT( ! is_complete() );
         BOOST_ASSERT( ! other->is_complete() );
 
-        typename symmetric_coroutine_impl< X >::param_type to( & x);
+        typename symmetric_coroutine_impl< X >::param_type to( const_cast< X * >( & x) );
         return yield_to_( other, & to);
     }
 
     template< typename X >
-    R * yield_to( symmetric_coroutine_impl< X & > * other, X & x)
+    R * yield_to( symmetric_coroutine_impl< X & > * other, X const& x)
     {
         BOOST_ASSERT( ! is_complete() );
         BOOST_ASSERT( ! other->is_complete() );
 
-        typename symmetric_coroutine_impl< X & >::param_type to( & x);
+        typename symmetric_coroutine_impl< X & >::param_type to( const_cast< X * >( & x) );
         return yield_to_( other, & to);
     }
 
@@ -281,22 +281,22 @@ public:
     }
 
     template< typename X >
-    R * yield_to( symmetric_coroutine_impl< X > * other, X x)
+    R * yield_to( symmetric_coroutine_impl< X > * other, X const& x)
     {
         BOOST_ASSERT( ! is_complete() );
         BOOST_ASSERT( ! other->is_complete() );
 
-        typename symmetric_coroutine_impl< X >::param_type to( & x);
+        typename symmetric_coroutine_impl< X >::param_type to( const_cast< X * >( & x) );
         return yield_to_( other, & to);
     }
 
     template< typename X >
-    R * yield_to( symmetric_coroutine_impl< X & > * other, X & x)
+    R * yield_to( symmetric_coroutine_impl< X & > * other, X const& x)
     {
         BOOST_ASSERT( ! is_complete() );
         BOOST_ASSERT( ! other->is_complete() );
 
-        typename symmetric_coroutine_impl< X & >::param_type to( & x);
+        typename symmetric_coroutine_impl< X & >::param_type to( const_cast< X * >( & x) );
         return yield_to_( other, & to);
     }
 
@@ -418,12 +418,22 @@ public:
     }
 
     template< typename X >
-    void yield_to( symmetric_coroutine_impl< X & > * other, X & x)
+    void yield_to( symmetric_coroutine_impl< X > * other, X const& x)
     {
         BOOST_ASSERT( ! is_complete() );
         BOOST_ASSERT( ! other->is_complete() );
 
-        typename symmetric_coroutine_impl< X & >::param_type to( & x);
+        typename symmetric_coroutine_impl< X >::param_type to( const_cast< X * >( & x) );
+        yield_to_( other, & to);
+    }
+
+    template< typename X >
+    void yield_to( symmetric_coroutine_impl< X & > * other, X const& x)
+    {
+        BOOST_ASSERT( ! is_complete() );
+        BOOST_ASSERT( ! other->is_complete() );
+
+        typename symmetric_coroutine_impl< X & >::param_type to( const_cast< X * >( & x) );
         yield_to_( other, & to);
     }
 
diff --git a/include/boost/coroutine/detail/symmetric_coroutine_yield.hpp b/include/boost/coroutine/detail/symmetric_coroutine_yield.hpp
index 621ded2..3079621 100644
--- a/include/boost/coroutine/detail/symmetric_coroutine_yield.hpp
+++ b/include/boost/coroutine/detail/symmetric_coroutine_yield.hpp
@@ -12,6 +12,8 @@
 #include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <boost/move/move.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/utility/enable_if.hpp>
 #include <boost/utility/explicit_operator_bool.hpp>
 
 #include <boost/coroutine/detail/config.hpp>
@@ -38,6 +40,8 @@ private:
     typedef parameters< R >                     param_type;
     typedef symmetric_coroutine_impl< R >       impl_type;
 
+    struct dummy {};
+
     BOOST_MOVABLE_BUT_NOT_COPYABLE( symmetric_coroutine_yield)
 
     impl_type   *   impl_;
@@ -86,7 +90,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type & x)
+    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type const& x,
+                                            typename disable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);
 
@@ -95,7 +103,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other)
+    symmetric_coroutine_yield & operator()( Coro & other,
+                                            typename enable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);
 
@@ -171,7 +183,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type & x)
+    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type const& x,
+                                            typename disable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);
 
@@ -180,7 +196,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other)
+    symmetric_coroutine_yield & operator()( Coro & other,
+                                            typename enable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);
 
@@ -206,6 +226,8 @@ private:
     typedef parameters< void >                  param_type;
     typedef symmetric_coroutine_impl< void >    impl_type;
 
+    struct dummy {};
+
     BOOST_MOVABLE_BUT_NOT_COPYABLE( symmetric_coroutine_yield)
 
     impl_type   *   impl_;
@@ -245,7 +267,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type & x)
+    symmetric_coroutine_yield & operator()( Coro & other, typename Coro::value_type const& x,
+                                            typename disable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);
 
@@ -254,7 +280,11 @@ public:
     }
 
     template< typename Coro >
-    symmetric_coroutine_yield & operator()( Coro & other)
+    symmetric_coroutine_yield & operator()( Coro & other,
+                                            typename enable_if<
+                                                is_same< typename Coro::value_type, void >,
+                                                dummy*
+                                            >::type = 0)
     {
         BOOST_ASSERT( other);