diff --git a/ipdb/__main__.py b/ipdb/__main__.py
index 3965725..beee6c9 100644
--- a/ipdb/__main__.py
+++ b/ipdb/__main__.py
@@ -8,7 +8,7 @@
 import os
 import sys
 
-from contextlib import contextmanager
+from decorator import contextmanager
 
 __version__ = '0.13.8.dev0'
 
@@ -228,27 +228,8 @@ def launch_ipdb_on_exception():
         pass
 
 
-class Decontext(object):
-    """
-    Makes a context manager also act as decorator.
-    """
-    def __init__(self, context_manager):
-        self._cm = context_manager
-
-    def __enter__(self):
-        return self._cm.__enter__()
-
-    def __exit__(self, *args, **kwds):
-        return self._cm.__exit__(*args, **kwds)
-
-    def __call__(self, func):
-        def wrapper(*args, **kwds):
-            with self:
-                return func(*args, **kwds)
-        return wrapper
-
-
-iex = Decontext(launch_ipdb_on_exception())
+# iex is a concise alias
+iex = launch_ipdb_on_exception()
 
 
 _usage = """\
diff --git a/setup.py b/setup.py
index 60b249f..6d2344c 100644
--- a/setup.py
+++ b/setup.py
@@ -61,6 +61,7 @@
               'toml >= 0.10.2'
           ],
           # No support for python 3.0, 3.1, 3.2.
+          # decorator is also a dependency of Ipython.
           ':python_version == "3.4"': ['ipython >= 6.0.0, < 7.0.0', 'toml >= 0.10.2', 'decorator < 5.0.0'],
           ':python_version == "3.5"': ['ipython >= 7.0.0, < 7.10.0', 'toml >= 0.10.2'],
           ':python_version == "3.6"': ['ipython >= 7.10.0, < 7.17.0', 'toml >= 0.10.2'],