diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 83e8ee2722ed8a..f17ff137b60d63 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -431,7 +431,9 @@ If not specified, then the field width will be determined by the content.
 When no explicit alignment is given, preceding the *width* field by a zero
 (``'0'``) character enables sign-aware zero-padding for numeric types,
 excluding :class:`complex`.  This is equivalent to a *fill* character of
-``'0'`` with an *alignment* type of ``'='``.
+``'0'`` with an *alignment* type of ``'='``.  If the *grouping* option for
+the integral part is used, a digit group separator is also inserted between
+leading zeros.
 
 .. versionchanged:: 3.10
    Preceding the *width* field by ``'0'`` no longer affects the default