Update C API docs for PEP 393.
diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index f6b105a..c6dfdf7 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -686,7 +686,7 @@
Py_ssize_t start,
Py_ssize_t end);
-/* Copy the string into a UCS4 buffer including the null character is copy_null
+/* Copy the string into a UCS4 buffer including the null character if copy_null
is set. Return NULL and raise an exception on error. Raise a ValueError if
the buffer is smaller than the string. Return buffer on success.