diff --git a/Lib/test/test_format.py b/Lib/test/test_format.py
index 70e748f..dc324af 100644
--- a/Lib/test/test_format.py
+++ b/Lib/test/test_format.py
@@ -289,10 +289,18 @@
         except locale.Error as err:
             self.skipTest("Cannot set locale: {}".format(err))
         try:
-            sep = locale.localeconv()['thousands_sep']
+            localeconv = locale.localeconv()
+            sep = localeconv['thousands_sep']
+            point = localeconv['decimal_point']
+
             text = format(123456789, "n")
             self.assertIn(sep, text)
             self.assertEqual(text.replace(sep, ''), '123456789')
+
+            text = format(1234.5, "n")
+            self.assertIn(sep, text)
+            self.assertIn(point, text)
+            self.assertEqual(text.replace(sep, ''), '1234' + point + '5')
         finally:
             locale.setlocale(locale.LC_ALL, oldloc)
 
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 2841b07..7753c32 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -9176,9 +9176,16 @@
     thousands_sep_data = PyUnicode_DATA(thousands_sep);
     thousands_sep_len = PyUnicode_GET_LENGTH(thousands_sep);
     if (unicode != NULL && thousands_sep_kind != kind) {
-        thousands_sep_data = _PyUnicode_AsKind(thousands_sep, kind);
-        if (!thousands_sep_data)
-            return -1;
+        if (thousands_sep_kind < kind) {
+            thousands_sep_data = _PyUnicode_AsKind(thousands_sep, kind);
+            if (!thousands_sep_data)
+                return -1;
+        }
+        else {
+            data = _PyUnicode_AsKind(unicode, thousands_sep_kind);
+            if (!data)
+                return -1;
+        }
     }
 
     switch (kind) {
@@ -9210,8 +9217,12 @@
         assert(0);
         return -1;
     }
-    if (unicode != NULL && thousands_sep_kind != kind)
-        PyMem_Free(thousands_sep_data);
+    if (unicode != NULL && thousands_sep_kind != kind) {
+        if (thousands_sep_kind < kind)
+            PyMem_Free(thousands_sep_data);
+        else
+            PyMem_Free(data);
+    }
     if (unicode == NULL) {
         *maxchar = 127;
         if (len != n_digits) {
diff --git a/Python/formatter_unicode.c b/Python/formatter_unicode.c
index 94f8047..58e66e0 100644
--- a/Python/formatter_unicode.c
+++ b/Python/formatter_unicode.c
@@ -529,6 +529,9 @@
     if (spec->n_lpadding || spec->n_spadding || spec->n_rpadding)
         *maxchar = Py_MAX(*maxchar, format->fill_char);
 
+    if (spec->n_decimal)
+        *maxchar = Py_MAX(*maxchar, PyUnicode_MAX_CHAR_VALUE(locale->decimal_point));
+
     return spec->n_lpadding + spec->n_sign + spec->n_prefix +
         spec->n_spadding + spec->n_grouped_digits + spec->n_decimal +
         spec->n_remainder + spec->n_rpadding;
@@ -548,10 +551,7 @@
     Py_ssize_t d_pos = d_start;
     unsigned int kind = PyUnicode_KIND(out);
     void *data = PyUnicode_DATA(out);
-
-#ifndef NDEBUG
     Py_ssize_t r;
-#endif
 
     if (spec->n_lpadding) {
         PyUnicode_Fill(out, pos, pos + spec->n_lpadding, fill_char);
@@ -593,18 +593,15 @@
             if (pdigits == NULL)
                 return -1;
         }
-#ifndef NDEBUG
-        r =
-#endif
-            _PyUnicode_InsertThousandsGrouping(
+        r = _PyUnicode_InsertThousandsGrouping(
                 out, pos,
                 spec->n_grouped_digits,
                 pdigits + kind * d_pos,
                 spec->n_digits, spec->n_min_width,
                 locale->grouping, locale->thousands_sep, NULL);
-#ifndef NDEBUG
+        if (r == -1)
+            return -1;
         assert(r == spec->n_grouped_digits);
-#endif
         if (PyUnicode_KIND(digits) < kind)
             PyMem_Free(pdigits);
         d_pos += spec->n_digits;