Fixed documentation of functions with const char* arguments.
diff --git a/Doc/c-api/mapping.rst b/Doc/c-api/mapping.rst
index 2803fd0..e341047 100644
--- a/Doc/c-api/mapping.rst
+++ b/Doc/c-api/mapping.rst
@@ -34,7 +34,7 @@
failure. This is equivalent to the Python statement ``del o[key]``.
-.. c:function:: int PyMapping_HasKeyString(PyObject *o, char *key)
+.. c:function:: int PyMapping_HasKeyString(PyObject *o, const char *key)
On success, return ``1`` if the mapping object has the key *key* and ``0``
otherwise. This is equivalent to the Python expression ``key in o``.