diff --git a/src/locale.cpp b/src/locale.cpp
index 00eb574..ca0a1c9 100644
--- a/src/locale.cpp
+++ b/src/locale.cpp
@@ -4379,7 +4379,9 @@
 __check_grouping(const string& __grouping, unsigned* __g, unsigned* __g_end,
                  ios_base::iostate& __err)
 {
-    if (__grouping.size() != 0)
+//  if the grouping pattern is empty _or_ there are no grouping bits, then do nothing
+//  we always have at least a single entry in [__g, __g_end); the end of the input sequence
+	if (__grouping.size() >= 0 && __g_end - __g > 1)
     {
         reverse(__g, __g_end);
         const char* __ig = __grouping.data();
diff --git a/test/std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long.pass.cpp b/test/std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long.pass.cpp
index 4212626..00b0c3a 100644
--- a/test/std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long.pass.cpp
+++ b/test/std/localization/locale.categories/category.numeric/locale.num.get/facet.num.get.members/get_long.pass.cpp
@@ -162,14 +162,14 @@
     ios.imbue(std::locale(std::locale(), new my_numpunct));
     {
         v = -1;
-        const char str[] = "123";
+        const char str[] = "123"; // no separators at all
         std::ios_base::iostate err = ios.goodbit;
         input_iterator<const char*> iter =
             f.get(input_iterator<const char*>(str),
                   input_iterator<const char*>(str+sizeof(str)),
                   ios, err, v);
         assert(iter.base() == str+sizeof(str)-1);
-        assert(err == ios.failbit);
+        assert(err == ios.goodbit);
         assert(v == 123);
     }
     {