diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_ru_RU.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_ru_RU.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_ru_RU.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_ru_RU.pass.cpp
@@ -11,6 +11,8 @@
 
 // REQUIRES: locale.ru_RU.UTF-8
 
+// XFAIL: glibc-old-ru_RU-decimal-point
+
 // <locale>
 
 // class money_get<charT, InputIterator>
diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_ru_RU.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_ru_RU.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_ru_RU.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_ru_RU.pass.cpp
@@ -11,6 +11,8 @@
 
 // REQUIRES: locale.ru_RU.UTF-8
 
+// XFAIL: glibc-old-ru_RU-decimal-point
+
 // <locale>
 
 // class money_put<charT, OutputIterator>
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -105,6 +105,18 @@
             }
           """)),
 
+  # Check for Glibc < 2.27, where the ru_RU.UTF-8 locale had
+  # mon_decimal_point == ".", which our tests don't handle.
+  Feature(name='glibc-old-ru_RU-decimal-point',
+          when=lambda cfg: not '_LIBCPP_HAS_NO_LOCALIZATION' in compilerMacros(cfg) and not programSucceeds(cfg, """
+            #include <locale.h>
+            #include <string.h>
+            int main(int, char**) {
+              setlocale(LC_ALL, "ru_RU.UTF-8");
+              return strcmp(localeconv()->mon_decimal_point, ",");
+            }
+          """)),
+
   # Whether Bash can run on the executor.
   # This is not always the case, for example when running on embedded systems.
   #