diff --git a/doc/history.qbk b/doc/history.qbk
index b3818c8f..4f2e012d 100644
--- a/doc/history.qbk
+++ b/doc/history.qbk
@@ -26,6 +26,7 @@ this gets bumped up from v4 to v5.
 * Fixed bug in collation code that failed if the locale generated collation strings with embedded nul's,
 see [@https://svn.boost.org/trac/boost/ticket/9451 #9451].
 * Apply patch for unusual thread usage (no statically initiallized mutexes), see [@https://svn.boost.org/trac/boost/ticket/9461 #9461].
+* Added better checks for invalid UTF-8 sequences, see [@https://svn.boost.org/trac/boost/ticket/9473 #9473].
 
 [h4 Boost-1.54]
 
diff --git a/doc/html/boost_regex/background_information/history.html b/doc/html/boost_regex/background_information/history.html
index 986d5019..b40b73ef 100644
--- a/doc/html/boost_regex/background_information/history.html
+++ b/doc/html/boost_regex/background_information/history.html
@@ -59,6 +59,13 @@
             Fixed bug in collation code that failed if the locale generated collation
             strings with embedded nul's, see <a href="https://svn.boost.org/trac/boost/ticket/9451" target="_top">#9451</a>.
           </li>
+<li class="listitem">
+            Apply patch for unusual thread usage (no statically initiallized mutexes),
+            see <a href="https://svn.boost.org/trac/boost/ticket/9461" target="_top">#9461</a>.
+          </li>
+<li class="listitem">
+            Added better checks for invalid UTF-8 sequences, see <a href="https://svn.boost.org/trac/boost/ticket/9473" target="_top">#9473</a>.
+          </li>
 </ul></div>
 <h5>
 <a name="boost_regex.background_information.history.h1"></a>
diff --git a/doc/html/index.html b/doc/html/index.html
index 1bcf8ef9..19acfe92 100644
--- a/doc/html/index.html
+++ b/doc/html/index.html
@@ -198,7 +198,7 @@
   </p>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: December 18, 2013 at 17:16:00 GMT</small></p></td>
+<td align="left"><p><small>Last revised: December 19, 2013 at 10:47:27 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>
diff --git a/include/boost/regex/pending/unicode_iterator.hpp b/include/boost/regex/pending/unicode_iterator.hpp
index 89afdd9d..b84cfa07 100644
--- a/include/boost/regex/pending/unicode_iterator.hpp
+++ b/include/boost/regex/pending/unicode_iterator.hpp
@@ -629,9 +629,15 @@ private:
          0x1FFFFFu,
       };
       m_value &= masks[extra];
-      // check the result:
+      // check the result is in range:
       if(m_value > static_cast<U32Type>(0x10FFFFu))
          invalid_sequence();
+      // The result must not be a surrogate:
+      if((m_value >= static_cast<U32Type>(0xD800)) && (m_value <= static_cast<U32Type>(0xDFFF)))
+         invalid_sequence();
+      // We should not have had an invalidly encoded UTF8 sequence:
+      if((extra > 0) && (m_value <= static_cast<U32Type>(masks[extra - 1])))
+         invalid_sequence();
    }
    BaseIterator m_position;
    mutable U32Type m_value;
diff --git a/test/unicode/unicode_iterator_test.cpp b/test/unicode/unicode_iterator_test.cpp
index d6156817..206b748b 100644
--- a/test/unicode/unicode_iterator_test.cpp
+++ b/test/unicode/unicode_iterator_test.cpp
@@ -108,6 +108,46 @@ void spot_checks()
    BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const boost::uint8_t*>(bad_seq3, bad_seq3, bad_seq3 + 5), boost::u8_to_u32_iterator<const boost::uint8_t*>(bad_seq3 + 5, bad_seq3, bad_seq3 + 5)), std::out_of_range);
    boost::uint8_t bad_seq4[5] = { '.', '*', 0xf6, '.', '*' };
    BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const boost::uint8_t*>(bad_seq4, bad_seq4, bad_seq4 + 5), boost::u8_to_u32_iterator<const boost::uint8_t*>(bad_seq4 + 5, bad_seq4, bad_seq4 + 5)), std::out_of_range);
+
+   // Invalid sequences containing surrogate pairs:
+   const char* invalid_pseq = "\xed\xa0\x80"; // single lowest lead surrogate U+D800
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xed\xb0\x80"; // single lowest trail surrogate U+DC00
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xed\xb0\x80"; // single lowest trail surrogate U+DC00
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xed\xbf\xbf"; // single highest trail surrogate U+DFFF
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+
+   // overlong encodings (created by left-padding with zero bits)
+   invalid_pseq = "\xc0\x80"; // illegal 2-byte encoding of 1-byte character U+0000
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xe0\x80\x80"; // illegal 3-byte encoding of 1-byte character U+0000
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xf0\x80\x80\x80"; // illegal 4-byte encoding of 1-byte character U+0000
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+
+   invalid_pseq = "\xc1\xbf"; // illegal 2-byte encoding of 1-byte character U+007F
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xe0\x81\xbf"; // illegal 3-byte encoding of 1-byte character U+007F
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xf0\x80\x81\xbf"; // illegal 4-byte encoding of 1-byte character U+007F
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+
+   invalid_pseq = "\xe0\x82\x80"; // illegal 3-byte encoding of 2-byte character U+0080
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xf0\x80\x82\x80"; // illegal 4-byte encoding of 2-byte character U+0080
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+
+   invalid_pseq = "\xe0\x9f\xbf"; // illegal 3-byte encoding of 2-byte character U+07FF
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xf0\x80\x9f\xbf"; // illegal 4-byte encoding of 2-byte character U+07FF
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+
+   invalid_pseq = "\xf0\x80\xa0\x80"; // illegal 4-byte encoding of 3-byte character U+0800
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
+   invalid_pseq = "\xf0\x8f\xbf\xbf"; // illegal 4-byte encoding of 3-byte character U+FFFF
+   BOOST_CHECK_THROW(iterate_over(boost::u8_to_u32_iterator<const char*>(invalid_pseq, invalid_pseq, invalid_pseq + std::strlen(invalid_pseq)), boost::u8_to_u32_iterator<const char*>(invalid_pseq + std::strlen(invalid_pseq), invalid_pseq, invalid_pseq + std::strlen(invalid_pseq))), std::out_of_range);
 }
 
 void test(const std::vector< ::boost::uint32_t>& v)