diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 1faabe4..7ea8668 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -128,7 +128,6 @@
 import time
 import traceback
 import warnings
-from inspect import isabstract
 
 # I see no other way to suppress these warnings;
 # putting them in test_grammar.py has no effect:
@@ -630,7 +629,7 @@
 
 def dash_R(the_module, test, indirect_test, huntrleaks):
     # This code is hackish and inelegant, but it seems to do the job.
-    import copy_reg, _abcoll
+    import copy_reg, _abcoll, io
 
     if not hasattr(sys, 'gettotalrefcount'):
         raise Exception("Tracking reference leaks requires a debug build "
@@ -641,8 +640,10 @@
     ps = copy_reg.dispatch_table.copy()
     pic = sys.path_importer_cache.copy()
     abcs = {}
-    for abc in [getattr(_abcoll, a) for a in _abcoll.__all__]:
-        if not isabstract(abc):
+    modules = _abcoll, io
+    for abc in [getattr(mod, a) for mod in modules for a in mod.__all__]:
+        # XXX isinstance(abc, ABCMeta) leads to infinite recursion
+        if not hasattr(abc, '_abc_registry'):
             continue
         for obj in abc.__subclasses__() + [abc]:
             abcs[obj] = obj._abc_registry.copy()
@@ -679,7 +680,7 @@
     import gc, copy_reg
     import _strptime, linecache, dircache
     import urlparse, urllib, urllib2, mimetypes, doctest
-    import struct, filecmp, _abcoll
+    import struct, filecmp
     from distutils.dir_util import _path_created
 
     # Restore some original values.
@@ -693,13 +694,10 @@
     sys._clear_type_cache()
 
     # Clear ABC registries, restoring previously saved ABC registries.
-    for abc in [getattr(_abcoll, a) for a in _abcoll.__all__]:
-        if not isabstract(abc):
-            continue
-        for obj in abc.__subclasses__() + [abc]:
-            obj._abc_registry = abcs.get(obj, {}).copy()
-            obj._abc_cache.clear()
-            obj._abc_negative_cache.clear()
+    for abc, registry in abcs.items():
+        abc._abc_registry = registry.copy()
+        abc._abc_cache.clear()
+        abc._abc_negative_cache.clear()
 
     # Clear assorted module caches.
     _path_created.clear()