diff --git a/developer-workflow/c-api.rst b/developer-workflow/c-api.rst
index 103abe7b0..7b727a735 100644
--- a/developer-workflow/c-api.rst
+++ b/developer-workflow/c-api.rst
@@ -110,9 +110,11 @@ Guidelines for expanding/changing the public API
   fields, arguments and return values are well defined.
 
 - Functions returning ``PyObject *`` must return a valid pointer on success,
-  and ``NULL`` with an exception raised on error.
-  Most other API must return ``-1`` with an exception raised on error,
-  and ``0`` on success.
+  and ``NULL`` if and only if an exception is raised.
+  Other API must return an ``int``: return ``0`` on success,
+  and a negative value if and only if an exception is raised.
+  ``-1`` should be used as the error value;
+  the caller should use the C idiom ``if (func() < 0)`` to check for errors.
 
 - APIs with lesser and greater results must return ``0`` for the lesser result,
   and ``1`` for the greater result.