diff --git a/include/boost/thread/win32/mutex.hpp b/include/boost/thread/win32/mutex.hpp
index 50477329..eed19b34 100644
--- a/include/boost/thread/win32/mutex.hpp
+++ b/include/boost/thread/win32/mutex.hpp
@@ -161,6 +161,10 @@ namespace boost
             }
             void unlock()
             {
+                if(!locked())
+                {
+                    throw boost::lock_error();
+                }
                 m.unlock();
                 is_locked=false;
             }
diff --git a/test/test_lock_concept.cpp b/test/test_lock_concept.cpp
index c76a0c61..be698a67 100644
--- a/test/test_lock_concept.cpp
+++ b/test/test_lock_concept.cpp
@@ -117,6 +117,7 @@ boost::unit_test_framework::test_suite* init_unit_test_suite(int, char*[])
     test->add(BOOST_TEST_CASE((test_unlocked_after_unlock_called<boost::try_mutex,boost::try_mutex::scoped_lock>())));
     test->add(BOOST_TEST_CASE((test_locked_after_lock_called<boost::try_mutex,boost::try_mutex::scoped_lock>())));
     test->add(BOOST_TEST_CASE((test_throws_if_lock_called_when_already_locked<boost::try_mutex,boost::try_mutex::scoped_lock>())));
+    test->add(BOOST_TEST_CASE((test_throws_if_unlock_called_when_already_unlocked<boost::try_mutex,boost::try_mutex::scoped_lock>())));
 
     test->add(BOOST_TEST_CASE((test_initially_locked<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
     test->add(BOOST_TEST_CASE((test_initially_locked_with_bool_parameter_true<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
@@ -124,6 +125,7 @@ boost::unit_test_framework::test_suite* init_unit_test_suite(int, char*[])
     test->add(BOOST_TEST_CASE((test_unlocked_after_unlock_called<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
     test->add(BOOST_TEST_CASE((test_locked_after_lock_called<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
     test->add(BOOST_TEST_CASE((test_throws_if_lock_called_when_already_locked<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
+    test->add(BOOST_TEST_CASE((test_throws_if_unlock_called_when_already_unlocked<boost::try_mutex,boost::try_mutex::scoped_try_lock>())));
 
     return test;
 }