*** boost/regex/v4/basic_regex_parser.hpp.orig	2008-01-14 12:53:01.000000000 -0600
--- boost/regex/v4/basic_regex_parser.hpp	2008-01-14 12:57:25.000000000 -0600
*************** bool basic_regex_parser<charT, traits>::
*** 777,782 ****
--- 777,783 ----
        case syntax_element_restart_continue:
        case syntax_element_jump:
        case syntax_element_startmark:
+       case syntax_element_backstep:
           // can't legally repeat any of the above:
           fail(regex_constants::error_badrepeat, m_position - m_base);
           return false;
*************** bool basic_regex_parser<charT, traits>::
*** 1862,1867 ****
--- 1863,1869 ----
     if(markid == -4)
     {
        re_syntax_base* b = this->getaddress(expected_alt_point);
+       // Make sure we have exactly one alternative following this state:
        if(b->type != syntax_element_alt)
        {
           re_alt* alt = static_cast<re_alt*>(this->insert_state(expected_alt_point, syntax_element_alt, sizeof(re_alt)));
*************** bool basic_regex_parser<charT, traits>::
*** 1872,1877 ****
--- 1874,1888 ----
           fail(regex_constants::error_bad_pattern, m_position - m_base);
           return false;
        }
+       // check for invalid repetition of next state:
+       b = this->getaddress(expected_alt_point);
+       b = this->getaddress(static_cast<re_alt*>(b)->next.i, b);
+       if((b->type != syntax_element_assert_backref)
+          && (b->type != syntax_element_startmark))
+       {
+          fail(regex_constants::error_badrepeat, m_position - m_base);
+          return false;
+       }
     }
     //
     // append closing parenthesis state: