diff --git a/asio/src/tests/unit/system_timer.cpp b/asio/src/tests/unit/system_timer.cpp
index a20c08a..1525f90 100644
--- a/asio/src/tests/unit/system_timer.cpp
+++ b/asio/src/tests/unit/system_timer.cpp
@@ -23,8 +23,337 @@
 
 #include "unit_test.hpp"
 
+#if defined(ASIO_HAS_STD_CHRONO)
+
+#include "asio/io_service.hpp"
+#include "asio/thread.hpp"
+
+#if defined(ASIO_HAS_BOOST_BIND)
+# include <boost/bind.hpp>
+#else // defined(ASIO_HAS_BOOST_BIND)
+# include <functional>
+#endif // defined(ASIO_HAS_BOOST_BIND)
+
+#if defined(ASIO_HAS_BOOST_BIND)
+namespace bindns = boost;
+#else // defined(ASIO_HAS_BOOST_BIND)
+namespace bindns = std;
+#endif // defined(ASIO_HAS_BOOST_BIND)
+
+namespace chronons = std::chrono;
+
+void increment(int* count)
+{
+  ++(*count);
+}
+
+void decrement_to_zero(asio::system_timer* t, int* count)
+{
+  if (*count > 0)
+  {
+    --(*count);
+
+    int before_value = *count;
+
+    t->expires_at(t->expires_at() + chronons::seconds(1));
+    t->async_wait(bindns::bind(decrement_to_zero, t, count));
+
+    // Completion cannot nest, so count value should remain unchanged.
+    ASIO_CHECK(*count == before_value);
+  }
+}
+
+void increment_if_not_cancelled(int* count,
+    const asio::error_code& ec)
+{
+  if (!ec)
+    ++(*count);
+}
+
+void cancel_timer(asio::system_timer* t)
+{
+  std::size_t num_cancelled = t->cancel();
+  ASIO_CHECK(num_cancelled == 1);
+}
+
+void cancel_one_timer(asio::system_timer* t)
+{
+  std::size_t num_cancelled = t->cancel_one();
+  ASIO_CHECK(num_cancelled == 1);
+}
+
+asio::system_timer::time_point now()
+{
+  return asio::system_timer::clock_type::now();
+}
+
+void system_timer_test()
+{
+  using chronons::seconds;
+  using chronons::microseconds;
+#if !defined(ASIO_HAS_BOOST_BIND)
+  using std::placeholders::_1;
+  using std::placeholders::_2;
+#endif // !defined(ASIO_HAS_BOOST_BIND)
+
+  asio::io_service ios;
+  int count = 0;
+
+  asio::system_timer::time_point start = now();
+
+  asio::system_timer t1(ios, seconds(1));
+  t1.wait();
+
+  // The timer must block until after its expiry time.
+  asio::system_timer::time_point end = now();
+  asio::system_timer::time_point expected_end = start + seconds(1);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  start = now();
+
+  asio::system_timer t2(ios, seconds(1) + microseconds(500000));
+  t2.wait();
+
+  // The timer must block until after its expiry time.
+  end = now();
+  expected_end = start + seconds(1) + microseconds(500000);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  t2.expires_at(t2.expires_at() + seconds(1));
+  t2.wait();
+
+  // The timer must block until after its expiry time.
+  end = now();
+  expected_end += seconds(1);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  start = now();
+
+  t2.expires_from_now(seconds(1) + microseconds(200000));
+  t2.wait();
+
+  // The timer must block until after its expiry time.
+  end = now();
+  expected_end = start + seconds(1) + microseconds(200000);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  start = now();
+
+  asio::system_timer t3(ios, seconds(5));
+  t3.async_wait(bindns::bind(increment, &count));
+
+  // No completions can be delivered until run() is called.
+  ASIO_CHECK(count == 0);
+
+  ios.run();
+
+  // The run() call will not return until all operations have finished, and
+  // this should not be until after the timer's expiry time.
+  ASIO_CHECK(count == 1);
+  end = now();
+  expected_end = start + seconds(1);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  count = 3;
+  start = now();
+
+  asio::system_timer t4(ios, seconds(1));
+  t4.async_wait(bindns::bind(decrement_to_zero, &t4, &count));
+
+  // No completions can be delivered until run() is called.
+  ASIO_CHECK(count == 3);
+
+  ios.reset();
+  ios.run();
+
+  // The run() call will not return until all operations have finished, and
+  // this should not be until after the timer's final expiry time.
+  ASIO_CHECK(count == 0);
+  end = now();
+  expected_end = start + seconds(3);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  count = 0;
+  start = now();
+
+  asio::system_timer t5(ios, seconds(10));
+  t5.async_wait(bindns::bind(increment_if_not_cancelled, &count, _1));
+  asio::system_timer t6(ios, seconds(1));
+  t6.async_wait(bindns::bind(cancel_timer, &t5));
+
+  // No completions can be delivered until run() is called.
+  ASIO_CHECK(count == 0);
+
+  ios.reset();
+  ios.run();
+
+  // The timer should have been cancelled, so count should not have changed.
+  // The total run time should not have been much more than 1 second (and
+  // certainly far less than 10 seconds).
+  ASIO_CHECK(count == 0);
+  end = now();
+  expected_end = start + seconds(2);
+  ASIO_CHECK(end < expected_end);
+
+  // Wait on the timer again without cancelling it. This time the asynchronous
+  // wait should run to completion and increment the counter.
+  t5.async_wait(bindns::bind(increment_if_not_cancelled, &count, _1));
+
+  ios.reset();
+  ios.run();
+
+  // The timer should not have been cancelled, so count should have changed.
+  // The total time since the timer was created should be more than 10 seconds.
+  ASIO_CHECK(count == 1);
+  end = now();
+  expected_end = start + seconds(10);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+
+  count = 0;
+  start = now();
+
+  // Start two waits on a timer, one of which will be cancelled. The one
+  // which is not cancelled should still run to completion and increment the
+  // counter.
+  asio::system_timer t7(ios, seconds(3));
+  t7.async_wait(bindns::bind(increment_if_not_cancelled, &count, _1));
+  t7.async_wait(bindns::bind(increment_if_not_cancelled, &count, _1));
+  asio::system_timer t8(ios, seconds(1));
+  t8.async_wait(bindns::bind(cancel_one_timer, &t7));
+
+  ios.reset();
+  ios.run();
+
+  // One of the waits should not have been cancelled, so count should have
+  // changed. The total time since the timer was created should be more than 3
+  // seconds.
+  ASIO_CHECK(count == 1);
+  end = now();
+  expected_end = start + seconds(3);
+  ASIO_CHECK(expected_end < end || expected_end == end);
+}
+
+void timer_handler(const asio::error_code&)
+{
+}
+
+void system_timer_cancel_test()
+{
+  static asio::io_service io_service;
+  struct timer
+  {
+    asio::system_timer t;
+    timer() : t(io_service)
+    {
+      t.expires_at(asio::system_timer::time_point::max());
+    }
+  } timers[50];
+
+  timers[2].t.async_wait(&timer_handler);
+  timers[41].t.async_wait(&timer_handler);
+  for (int i = 10; i < 20; ++i)
+    timers[i].t.async_wait(&timer_handler);
+
+  ASIO_CHECK(timers[2].t.cancel() == 1);
+  ASIO_CHECK(timers[41].t.cancel() == 1);
+  for (int i = 10; i < 20; ++i)
+    ASIO_CHECK(timers[i].t.cancel() == 1);
+}
+
+struct custom_allocation_timer_handler
+{
+  custom_allocation_timer_handler(int* count) : count_(count) {}
+  void operator()(const asio::error_code&) {}
+  int* count_;
+};
+
+void* asio_handler_allocate(std::size_t size,
+    custom_allocation_timer_handler* handler)
+{
+  ++(*handler->count_);
+  return ::operator new(size);
+}
+
+void asio_handler_deallocate(void* pointer, std::size_t,
+    custom_allocation_timer_handler* handler)
+{
+  --(*handler->count_);
+  ::operator delete(pointer);
+}
+
+void system_timer_custom_allocation_test()
+{
+  static asio::io_service io_service;
+  struct timer
+  {
+    asio::system_timer t;
+    timer() : t(io_service) {}
+  } timers[100];
+
+  int allocation_count = 0;
+
+  for (int i = 0; i < 50; ++i)
+  {
+    timers[i].t.expires_at(asio::system_timer::time_point::max());
+    timers[i].t.async_wait(custom_allocation_timer_handler(&allocation_count));
+  }
+
+  for (int i = 50; i < 100; ++i)
+  {
+    timers[i].t.expires_at(asio::system_timer::time_point::min());
+    timers[i].t.async_wait(custom_allocation_timer_handler(&allocation_count));
+  }
+
+  for (int i = 0; i < 50; ++i)
+    timers[i].t.cancel();
+
+  io_service.run();
+
+  ASIO_CHECK(allocation_count == 0);
+}
+
+void io_service_run(asio::io_service* ios)
+{
+  ios->run();
+}
+
+void system_timer_thread_test()
+{
+  asio::io_service ios;
+  asio::io_service::work w(ios);
+  asio::system_timer t1(ios);
+  asio::system_timer t2(ios);
+  int count = 0;
+
+  asio::thread th(bindns::bind(io_service_run, &ios));
+
+  t2.expires_from_now(chronons::seconds(2));
+  t2.wait();
+
+  t1.expires_from_now(chronons::seconds(2));
+  t1.async_wait(bindns::bind(increment, &count));
+
+  t2.expires_from_now(chronons::seconds(4));
+  t2.wait();
+
+  ios.stop();
+  th.join();
+
+  ASIO_CHECK(count == 1);
+}
+
+ASIO_TEST_SUITE
+(
+  "system_timer",
+  ASIO_TEST_CASE(system_timer_test)
+  ASIO_TEST_CASE(system_timer_cancel_test)
+  ASIO_TEST_CASE(system_timer_custom_allocation_test)
+  ASIO_TEST_CASE(system_timer_thread_test)
+)
+#else // defined(ASIO_HAS_STD_CHRONO)
 ASIO_TEST_SUITE
 (
   "system_timer",
   ASIO_TEST_CASE(null_test)
 )
+#endif // defined(ASIO_HAS_STD_CHRONO)