diff --git a/Python/fileutils.c b/Python/fileutils.c
index b3b7925..b77e490 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -1801,7 +1801,7 @@
     if (change_locale) {
         oldloc = setlocale(LC_CTYPE, NULL);
         if (!oldloc) {
-            PyErr_SetString(PyExc_RuntimeWarning, "faild to get LC_CTYPE locale");
+            PyErr_SetString(PyExc_RuntimeWarning, "failed to get LC_CTYPE locale");
             return -1;
         }
 
@@ -1817,7 +1817,7 @@
         }
 
         if (loc != NULL) {
-            /* Only set the locale temporarilty the LC_CTYPE locale
+            /* Only set the locale temporarily the LC_CTYPE locale
                if LC_NUMERIC locale is different than LC_CTYPE locale and
                decimal_point and/or thousands_sep are non-ASCII or longer than
                1 byte */
diff --git a/Python/formatter_unicode.c b/Python/formatter_unicode.c
index ba09cc6..2cd3eb8 100644
--- a/Python/formatter_unicode.c
+++ b/Python/formatter_unicode.c
@@ -396,9 +396,10 @@
     PyObject *decimal_point;
     PyObject *thousands_sep;
     const char *grouping;
+    char *grouping_buffer;
 } LocaleInfo;
 
-#define STATIC_LOCALE_INFO_INIT {0, 0, 0}
+#define STATIC_LOCALE_INFO_INIT {0, 0, 0, 0}
 
 /* describes the layout for an integer, see the comment in
    calc_number_widths() for details */
@@ -705,11 +706,22 @@
 {
     switch (type) {
     case LT_CURRENT_LOCALE: {
+        const char *grouping;
         if (_Py_GetLocaleconvNumeric(&locale_info->decimal_point,
                                      &locale_info->thousands_sep,
-                                     &locale_info->grouping) < 0) {
+                                     &grouping) < 0) {
             return -1;
         }
+
+        /* localeconv() grouping can become a dangling pointer or point
+           to a different string if another thread calls localeconv() during
+           the string formatting. Copy the string to avoid this risk. */
+        locale_info->grouping_buffer = _PyMem_Strdup(grouping);
+        if (locale_info->grouping_buffer == NULL) {
+            PyErr_NoMemory();
+            return -1;
+        }
+        locale_info->grouping = locale_info->grouping_buffer;
         break;
     }
     case LT_DEFAULT_LOCALE:
@@ -743,6 +755,7 @@
 {
     Py_XDECREF(locale_info->decimal_point);
     Py_XDECREF(locale_info->thousands_sep);
+    PyMem_Free(locale_info->grouping_buffer);
 }
 
 /************************************************************************/