document PyUnicode_CompareWithASCIIString
diff --git a/Doc/c-api/unicode.rst b/Doc/c-api/unicode.rst
index 653ee6e..e274591 100644
--- a/Doc/c-api/unicode.rst
+++ b/Doc/c-api/unicode.rst
@@ -869,6 +869,12 @@
    respectively.
 
 
+.. cfunction:: int PyUnicode_CompareWithASCIIString(PyObject *uni, char *string)
+
+   Compare a unicode object, *uni*, with *string* and return -1, 0, 1 for less
+   than, equal, and greater than, respectively.
+
+
 .. cfunction:: int PyUnicode_RichCompare(PyObject *left,  PyObject *right,  int op)
 
    Rich compare two unicode strings and return one of the following: