Index: libcxx/test/std/re/re.badexp/regex_error.pass.cpp
===================================================================
--- libcxx/test/std/re/re.badexp/regex_error.pass.cpp
+++ libcxx/test/std/re/re.badexp/regex_error.pass.cpp
@@ -25,72 +25,98 @@
     {
         std::regex_error e(std::regex_constants::error_collate);
         assert(e.code() == std::regex_constants::error_collate);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid collating element name."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_ctype);
         assert(e.code() == std::regex_constants::error_ctype);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid character class name."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_escape);
         assert(e.code() == std::regex_constants::error_escape);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid escaped character, or a "
                "trailing escape."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_backref);
         assert(e.code() == std::regex_constants::error_backref);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid back reference."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_brack);
         assert(e.code() == std::regex_constants::error_brack);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained mismatched [ and ]."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_paren);
         assert(e.code() == std::regex_constants::error_paren);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained mismatched ( and )."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_brace);
         assert(e.code() == std::regex_constants::error_brace);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained mismatched { and }."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_badbrace);
         assert(e.code() == std::regex_constants::error_badbrace);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid range in a {} expression."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_range);
         assert(e.code() == std::regex_constants::error_range);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The expression contained an invalid character range, "
                "such as [b-a] in most encodings."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_space);
         assert(e.code() == std::regex_constants::error_space);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("There was insufficient memory to convert the expression into "
                "a finite state machine."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_badrepeat);
         assert(e.code() == std::regex_constants::error_badrepeat);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("One of *?+{ was not preceded by a valid regular expression."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_complexity);
         assert(e.code() == std::regex_constants::error_complexity);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("The complexity of an attempted match against a regular "
                "expression exceeded a pre-set level."));
+#endif
     }
     {
         std::regex_error e(std::regex_constants::error_stack);
         assert(e.code() == std::regex_constants::error_stack);
+#ifdef _LIBCPP_VERSION
         assert(e.what() == std::string("There was insufficient memory to determine whether the regular "
                "expression could match the specified character sequence."));
+#endif
     }
 
   return 0;
Index: libcxx/test/std/re/re.const/re.synopt/syntax_option_type.pass.cpp
===================================================================
--- libcxx/test/std/re/re.const/re.synopt/syntax_option_type.pass.cpp
+++ libcxx/test/std/re/re.const/re.synopt/syntax_option_type.pass.cpp
@@ -38,7 +38,8 @@
     assert(std::regex_constants::nosubs != 0);
     assert(std::regex_constants::optimize != 0);
     assert(std::regex_constants::collate != 0);
-#ifdef _LIBCPP_ABI_REGEX_CONSTANTS_NONZERO  // https://llvm.org/PR35967
+#if defined _LIBCPP_ABI_REGEX_CONSTANTS_NONZERO || !defined _LIBCPP_VERSION
+    // https://llvm.org/PR35967
     assert(std::regex_constants::ECMAScript != 0);
 #else
     assert(std::regex_constants::ECMAScript == 0);