diff --git a/include/simulator/simulator.hpp b/include/simulator/simulator.hpp
index 8e02fa7..f789ab2 100644
--- a/include/simulator/simulator.hpp
+++ b/include/simulator/simulator.hpp
@@ -208,6 +208,10 @@ namespace sim
 			wait_read, wait_write, wait_error
 		};
 
+		// alias matching the name used by boost.asio's basic_socket::wait_type,
+		// for code that's written against both APIs
+		using wait_type = wait_type_t;
+
 		// io_control
 		using reuse_address = boost::asio::socket_base::reuse_address;
 		using executor_type = io_executor;
@@ -767,7 +771,7 @@ namespace sim
 				if (w == socket_base::wait_type_t::wait_write)
 				{
 					abort_send_handlers();
-					assert(false && "not supported yet");
+					async_wait_write_impl(std::move(handler));
 				}
 				else if (w == socket_base::wait_type_t::wait_read)
 				{
@@ -841,6 +845,8 @@ namespace sim
 				, aux::function<void(boost::system::error_code const&, std::size_t)> handler);
 			void async_wait_read_impl(
 				aux::function<void(boost::system::error_code const&)> handler);
+			void async_wait_write_impl(
+				aux::function<void(boost::system::error_code const&)> handler);
 			std::size_t write_some_impl(std::vector<asio::const_buffer> const& bufs
 				, boost::system::error_code& ec);
 			std::size_t read_some_impl(std::vector<asio::mutable_buffer> const& bufs
diff --git a/src/tcp_socket.cpp b/src/tcp_socket.cpp
index 918efc8..173de68 100644
--- a/src/tcp_socket.cpp
+++ b/src/tcp_socket.cpp
@@ -709,6 +709,37 @@ namespace ip {
 		m_recv_null_buffers = true;
 	}
 
+	void tcp::socket::async_wait_write_impl(
+		aux::function<void(boost::system::error_code const&)> handler)
+	{
+		if (!m_open)
+		{
+			boost::system::error_code const ec(error::bad_descriptor);
+			post(m_io_service, aux::make_malloc(std::bind(std::move(handler), ec)));
+			return;
+		}
+
+		if (!m_channel)
+		{
+			boost::system::error_code const ec(error::not_connected);
+			post(m_io_service, aux::make_malloc(std::bind(std::move(handler), ec)));
+			return;
+		}
+
+		if (!m_connect_handler && m_bytes_in_flight + m_mss <= m_cwnd)
+		{
+			// the socket is writable right now. complete immediately without
+			// actually writing anything, this is the null_buffers equivalent
+			// for writes
+			boost::system::error_code const ec;
+			post(m_io_service, aux::make_malloc(std::bind(std::move(handler), ec)));
+			return;
+		}
+
+		m_wait_send_handler = std::move(handler);
+		m_send_null_buffers = true;
+	}
+
 	// if there is an outstanding read operation, and this was the first incoming
 	// operation since we last drained, wake up the reader
 	void tcp::socket::maybe_wakeup_reader()
@@ -731,12 +762,11 @@ namespace ip {
 
 	void tcp::socket::maybe_wakeup_writer()
 	{
-		if (!m_send_handler) return;
+		if (!m_send_handler && !m_wait_send_handler) return;
 
 		if (m_send_null_buffers)
 		{
-			assert(false && "not supported yet");
-//			async_wait_write_impl(m_recv_handler);
+			async_wait_write_impl(std::move(m_wait_send_handler));
 		}
 		else
 		{