diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index 00ef005..18ff697 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -72,6 +72,9 @@
 
 .. c:function:: void PyErr_WriteUnraisable(PyObject *obj)
 
+   Call :func:`sys.unraisablehook` using the current exception and *obj*
+   argument.
+
    This utility function prints a warning message to ``sys.stderr`` when an
    exception has been set but it is impossible for the interpreter to actually
    raise the exception.  It is used, for example, when an exception occurs in an
@@ -81,6 +84,8 @@
    in which the unraisable exception occurred. If possible,
    the repr of *obj* will be printed in the warning message.
 
+   An exception must be set when calling this function.
+
 
 Raising exceptions
 ==================