Index: libcxx/include/regex
===================================================================
--- libcxx/include/regex
+++ libcxx/include/regex
@@ -5555,6 +5555,12 @@
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if (__flags & regex_constants::match_not_null &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 __m.__matches_[0].first = __first;
                 __m.__matches_[0].second = _VSTD::next(__first, __s.__current_ - __first);
                 __m.__matches_[0].matched = true;
@@ -5618,6 +5624,12 @@
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if (__flags & regex_constants::match_not_null &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                     __highest_j = __s.__current_ - __s.__first_;
                 __matched = true;
@@ -5703,6 +5715,12 @@
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if (__flags & regex_constants::match_not_null &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                 {
                     __highest_j = __s.__current_ - __s.__first_;
Index: libcxx/test/std/re/re.const/re.matchflag/match_not_null.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/re/re.const/re.matchflag/match_not_null.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <regex>
+
+// match_not_null:
+//     The regular expression shall not match an empty sequence.
+
+#include "test_macros.h"
+#include <cassert>
+#include <regex>
+
+int main()
+{
+  // When match_not_null is on, the regex engine should reject empty matches and
+  // move on to try other solutions.
+  std::cmatch m;
+  assert(!std::regex_search("a", m, std::regex("b*"),
+                            std::regex_constants::match_not_null));
+  assert(std::regex_search("aa", m, std::regex("a*?"),
+                           std::regex_constants::match_not_null));
+  assert(m[0].length() == 1);
+  assert(!std::regex_search("a", m, std::regex("b*", std::regex::extended),
+                            std::regex_constants::match_not_null));
+  assert(!std::regex_search(
+      "a", m,
+      std::regex("b*", std::regex::extended | std::regex_constants::nosubs),
+      std::regex_constants::match_not_null));
+}