Issue #15657: Merge other doc fix from 3.5
diff --git a/Doc/c-api/structures.rst b/Doc/c-api/structures.rst
index 3e8a90c..f481193 100644
--- a/Doc/c-api/structures.rst
+++ b/Doc/c-api/structures.rst
@@ -168,7 +168,7 @@
Methods with these flags must be of type :c:type:`PyCFunctionWithKeywords`.
The function expects three parameters: *self*, *args*, and a dictionary of
- all the keyword arguments. The flag is typically combined with
+ all the keyword arguments. The flag must be combined with
:const:`METH_VARARGS`, and the parameters are typically processed using
:c:func:`PyArg_ParseTupleAndKeywords`.