diff --git a/src/beast/modules/beast_core/functional/SharedFunction.h b/src/beast/modules/beast_core/functional/SharedFunction.h
index 9f2b416139..937942c929 100644
--- a/src/beast/modules/beast_core/functional/SharedFunction.h
+++ b/src/beast/modules/beast_core/functional/SharedFunction.h
@@ -25,6 +25,8 @@
 template <typename Signature, class Allocator = std::allocator <char> >
 class SharedFunction;
 
+//------------------------------------------------------------------------------
+
 // nullary function
 //
 template <typename R, class A>
@@ -61,6 +63,10 @@ public:
 
     //--------------------------------------------------------------------------
 
+    SharedFunction ()
+    {
+    }
+
     template <typename F>
     SharedFunction (F f, A a = A ())
         : m_ptr (::new (
@@ -86,8 +92,15 @@ public:
         return *this;
     }
 
-    R operator() ()
+    bool empty () const
     {
+        return m_ptr == nullptr;
+    }
+
+    R operator() () const
+    {
+        bassert (! empty());
+
         return (*m_ptr)();
     }
 
@@ -95,5 +108,88 @@ private:
     SharedPtr <Call> m_ptr;
 };
 
+//------------------------------------------------------------------------------
+
+// unary function (arity 1)
+//
+template <typename R, typename P1, class A>
+class SharedFunction <R (P1), A>
+{
+public:
+    class Call : public SharedObject
+    {
+    public:
+        virtual R operator() (P1 p1) = 0;
+    };
+
+    template <typename F>
+    class CallType : public Call
+    {
+    public:
+        typedef typename A:: template rebind <CallType <F> >::other Allocator;
+
+        CallType (BEAST_MOVE_ARG(F) f, A a = A ())
+            : m_f (BEAST_MOVE_CAST(F)(f))
+            , m_a (a)
+        {
+        }
+
+        R operator() (P1 p1)
+        {
+            return m_f (p1);
+        }
+
+    private:
+        F m_f;
+        Allocator m_a;
+    };
+
+    //--------------------------------------------------------------------------
+
+    SharedFunction ()
+    {
+    }
+
+    template <typename F>
+    SharedFunction (F f, A a = A ())
+        : m_ptr (::new (
+            typename CallType <F>::Allocator (a)
+                .allocate (sizeof (CallType <F>)))
+                    CallType <F> (BEAST_MOVE_CAST(F)(f), a))
+    {
+    }
+
+    SharedFunction (SharedFunction const& other)
+        : m_ptr (other.m_ptr)
+    {
+    }
+
+    SharedFunction (SharedFunction const& other, A)
+        : m_ptr (other.m_ptr)
+    {
+    }
+
+    SharedFunction& operator= (SharedFunction const& other)
+    {
+        m_ptr = other.m_ptr;
+        return *this;
+    }
+
+    bool empty () const
+    {
+        return m_ptr == nullptr;
+    }
+
+    R operator() (P1 p1) const
+    {
+        bassert (! empty());
+
+        return (*m_ptr)(p1);
+    }
+
+private:
+    SharedPtr <Call> m_ptr;
+};
+
 
 #endif