diff --git a/Include/stringobject.h b/Include/stringobject.h
index e3f880a..4057362 100644
--- a/Include/stringobject.h
+++ b/Include/stringobject.h
@@ -176,7 +176,17 @@
 				   (only possible for 0-terminated
 				   strings) */
     );
-    
+
+/* Using the current locale, insert the thousands grouping
+   into the string pointed to by buffer.  For the argument descriptions,
+   see Objects/stringlib/localeutil.h */
+
+PyAPI_FUNC(int) _PyString_InsertThousandsGrouping(char *buffer,
+						  Py_ssize_t len,
+						  char *plast,
+						  Py_ssize_t buf_size,
+						  Py_ssize_t *count,
+						  int append_zero_char);
 
 #ifdef __cplusplus
 }