diff --git a/include/boost/regex/v4/basic_regex_creator.hpp b/include/boost/regex/v4/basic_regex_creator.hpp
index 51704a84..2e98ae3c 100644
--- a/include/boost/regex/v4/basic_regex_creator.hpp
+++ b/include/boost/regex/v4/basic_regex_creator.hpp
@@ -399,9 +399,13 @@ re_syntax_base* basic_regex_creator<charT, traits>::append_set(
    last = char_set.singles_end();
    while(first != last)
    {
-      charT* p = static_cast<charT*>(this->m_pdata->m_data.extend(sizeof(charT) * (first->second ? 3 : 2)));
+      charT* p = static_cast<charT*>(this->m_pdata->m_data.extend(sizeof(charT) * (first->first ? 1 : first->second ? 3 : 2)));
       p[0] = m_traits.translate(first->first, m_icase);
-      if(first->second)
+      if(first->first)
+      {
+         p[0] = 0;
+      }
+      else if(first->second)
       {
          p[1] = m_traits.translate(first->second, m_icase);
          p[2] = 0;
diff --git a/include/boost/regex/v4/perl_matcher.hpp b/include/boost/regex/v4/perl_matcher.hpp
index 96a086b8..b1434d07 100644
--- a/include/boost/regex/v4/perl_matcher.hpp
+++ b/include/boost/regex/v4/perl_matcher.hpp
@@ -161,9 +161,9 @@ iterator BOOST_REGEX_CALL re_is_set_member(iterator next,
       if(*p == static_cast<charT>(0))
       {
          // treat null string as special case:
-         if(traits_inst.translate(*ptr, icase) != *p)
+         if(traits_inst.translate(*ptr, icase))
          {
-            while(*p == static_cast<charT>(0))++p;
+            ++p;
             continue;
          }
          return set_->isnot ? next : (ptr == next) ? ++next : ptr;