diff --git a/Lib/test/exception_hierarchy.txt b/Lib/test/exception_hierarchy.txt
index 064e8ca3802..e5ce8918f71 100644
--- a/Lib/test/exception_hierarchy.txt
+++ b/Lib/test/exception_hierarchy.txt
@@ -3,6 +3,7 @@ BaseException
  +-- KeyboardInterrupt
  +-- GeneratorExit
  +-- Exception
+      +-- BufferError
       +-- StopIteration
       +-- StandardError
       |    +-- ArithmeticError