diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
index 325a4219938..602e90914ed 100644
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -109,7 +109,7 @@ The :mod:`csv` module defines the following functions:
           spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])
 
 
-.. function:: register_dialect(name[, dialect], **fmtparams)
+.. function:: register_dialect(name[, dialect[, **fmtparams]])
 
    Associate *dialect* with *name*.  *name* must be a string. The
    dialect can be specified either by passing a sub-class of :class:`Dialect`, or
diff --git a/Modules/_csv.c b/Modules/_csv.c
index eb886264d7a..a614191ac6a 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -1588,7 +1588,7 @@ PyDoc_STRVAR(csv_get_dialect_doc,
 
 PyDoc_STRVAR(csv_register_dialect_doc,
 "Create a mapping from a string name to a dialect class.\n"
-"    dialect = csv.register_dialect(name, dialect)");
+"    dialect = csv.register_dialect(name[, dialect[, **fmtparams]])");
 
 PyDoc_STRVAR(csv_unregister_dialect_doc,
 "Delete the name/dialect mapping associated with a string name.\n"