diff -r 36af3566b67a Lib/test/test_traceback.py
--- a/Lib/test/test_traceback.py	Thu Nov 03 15:38:58 2016 +0200
+++ b/Lib/test/test_traceback.py	Thu Nov 03 21:36:10 2016 +0100
@@ -594,6 +594,12 @@
         err = self.get_report(Exception(''))
         self.assertIn('Exception\n', err)
 
+    def test_unhashable_exc(self):
+        class UnhashableException(Exception):
+            __hash__ = None
+        err = self.get_report(UnhashableException())
+        self.assertIn('UnhashableException', err)
+
 
 class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
     #
diff -r 36af3566b67a Lib/traceback.py
--- a/Lib/traceback.py	Thu Nov 03 15:38:58 2016 +0200
+++ b/Lib/traceback.py	Thu Nov 03 21:36:10 2016 +0100
@@ -459,11 +459,22 @@
         # Handle loops in __cause__ or __context__.
         if _seen is None:
             _seen = set()
-        _seen.add(exc_value)
+        try:
+            _seen.add(exc_value)
+        except TypeError:
+            pass
+        try:
+            cause_already_seen = exc_value.__cause__ in _seen
+        except TypeError:
+            cause_already_seen = True
+        try:
+            context_already_seen = exc_value.__context__ in _seen
+        except TypeError:
+            context_already_seen = True
         # Gracefully handle (the way Python 2.4 and earlier did) the case of
         # being called with no type or value (None, None, None).
         if (exc_value and exc_value.__cause__ is not None
-            and exc_value.__cause__ not in _seen):
+            and not cause_already_seen):
             cause = TracebackException(
                 type(exc_value.__cause__),
                 exc_value.__cause__,
@@ -475,7 +486,7 @@
         else:
             cause = None
         if (exc_value and exc_value.__context__ is not None
-            and exc_value.__context__ not in _seen):
+            and not context_already_seen):
             context = TracebackException(
                 type(exc_value.__context__),
                 exc_value.__context__,