diff --git a/Lib/test/exception_hierarchy.txt b/Lib/test/exception_hierarchy.txt
index 5e83faab9a6..f2649aa2d41 100644
--- a/Lib/test/exception_hierarchy.txt
+++ b/Lib/test/exception_hierarchy.txt
@@ -45,7 +45,6 @@ BaseException
       ├── StopAsyncIteration
       ├── StopIteration
       ├── SyntaxError
-      │    └── _IncompleteInputError
       │    └── IndentationError
       │         └── TabError
       ├── SystemError
diff --git a/Lib/test/test_baseexception.py b/Lib/test/test_baseexception.py
index 6dc06c5e4bc..e599b02c17d 100644
--- a/Lib/test/test_baseexception.py
+++ b/Lib/test/test_baseexception.py
@@ -78,6 +78,9 @@ class ExceptionClassTests(unittest.TestCase):
                 last_depth = depth
         finally:
             inheritance_tree.close()
+
+        # Underscore-prefixed (private) exceptions don't need to be documented
+        exc_set = set(e for e in exc_set if not e.startswith('_'))
         self.assertEqual(len(exc_set), 0, "%s not accounted for" % exc_set)
 
     interface_tests = ("length", "args", "str", "repr")