diff --git a/Lib/_weakrefset.py b/Lib/_weakrefset.py
new file mode 100644
index 00000000000..e56ac048dd5
--- /dev/null
+++ b/Lib/_weakrefset.py
@@ -0,0 +1,111 @@
+# Access WeakSet through the weakref module.
+# This code is separated-out because it is needed
+# by abc.py to load everything else at startup.
+
+from _weakref import ref
+
+__all__ = ['WeakSet']
+
+class WeakSet:
+    def __init__(self, data=None):
+        self.data = set()
+        def _remove(item, selfref=ref(self)):
+            self = selfref()
+            if self is not None:
+                self.data.discard(item)
+        self._remove = _remove
+        if data is not None:
+            self.update(data)
+
+    def __iter__(self):
+        for itemref in self.data:
+            item = itemref()
+            if item is not None:
+                yield item
+
+    def __contains__(self, item):
+        return ref(item) in self.data
+
+    def __reduce__(self):
+        return (self.__class__, (list(self),),
+                getattr(self, '__dict__', None))
+
+    def add(self, item):
+        self.data.add(ref(item, self._remove))
+
+    def clear(self):
+        self.data.clear()
+
+    def copy(self):
+        return self.__class__(self)
+
+    def pop(self):
+        while True:
+            itemref = self.data.pop()
+            item = itemref()
+            if item is not None:
+                return item
+
+    def remove(self, item):
+        self.data.remove(ref(item))
+
+    def discard(self, item):
+        self.data.discard(ref(item))
+
+    def update(self, other):
+        if isinstance(other, self.__class__):
+            self.data.update(other.data)
+        else:
+            for element in other:
+                self.add(element)
+    __ior__ = update
+
+    # Helper functions for simple delegating methods.
+    def _apply(self, other, method):
+        if not isinstance(other, self.__class__):
+            other = self.__class__(other)
+        newdata = method(other.data)
+        newset = self.__class__()
+        newset.data = newdata
+        return newset
+
+    def _apply_mutate(self, other, method):
+        if not isinstance(other, self.__class__):
+            other = self.__class__(other)
+        method(other)
+
+    def difference(self, other):
+        return self._apply(other, self.data.difference)
+    __sub__ = difference
+
+    def difference_update(self, other):
+        self._apply_mutate(self, self.data.difference_update)
+    __isub__ = difference_update
+
+    def intersection(self, other):
+        return self._apply(other, self.data.intersection)
+    __and__ = intersection
+
+    def intersection_update(self, other):
+        self._apply_mutate(self, self.data.intersection_update)
+    __iand__ = intersection_update
+
+    def issubset(self, other):
+        return self.data.issubset(ref(item) for item in other)
+    __lt__ = issubset
+
+    def issuperset(self, other):
+        return self.data.issuperset(ref(item) for item in other)
+    __gt__ = issuperset
+
+    def symmetric_difference(self, other):
+        return self._apply(other, self.data.symmetric_difference)
+    __xor__ = symmetric_difference
+
+    def symmetric_difference_update(self, other):
+        self._apply_mutate(other, self.data.symmetric_difference_update)
+    __ixor__ = symmetric_difference_update
+
+    def union(self, other):
+        self._apply_mutate(other, self.data.union)
+    __or__ = union
diff --git a/Lib/abc.py b/Lib/abc.py
index 875115361d8..8fb61c603c0 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -3,7 +3,7 @@
 
 """Abstract Base Classes (ABCs) according to PEP 3119."""
 
-from weakref import WeakSet
+from _weakrefset import WeakSet
 
 def abstractmethod(funcobj):
     """A decorator indicating abstract methods.
diff --git a/Lib/weakref.py b/Lib/weakref.py
index c54a0729d49..a9c05d82d94 100644
--- a/Lib/weakref.py
+++ b/Lib/weakref.py
@@ -20,12 +20,14 @@ from _weakref import (
      ProxyType,
      ReferenceType)
 
+from _weakrefset import WeakSet
 
 ProxyTypes = (ProxyType, CallableProxyType)
 
 __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
            "WeakKeyDictionary", "ReferenceType", "ProxyType",
-           "CallableProxyType", "ProxyTypes", "WeakValueDictionary"]
+           "CallableProxyType", "ProxyTypes", "WeakValueDictionary",
+           "WeakSet"]
 
 
 class WeakValueDictionary(UserDict.UserDict):
@@ -337,108 +339,3 @@ class WeakKeyDictionary(UserDict.UserDict):
                 d[ref(key, self._remove)] = value
         if len(kwargs):
             self.update(kwargs)
-
-
-class WeakSet:
-    def __init__(self, data=None):
-        self.data = set()
-        def _remove(item, selfref=ref(self)):
-            self = selfref()
-            if self is not None:
-                self.data.discard(item)
-        self._remove = _remove
-        if data is not None:
-            self.update(data)
-
-    def __iter__(self):
-        for itemref in self.data:
-            item = itemref()
-            if item is not None:
-                yield item
-
-    def __contains__(self, item):
-        return ref(item) in self.data
-
-    def __reduce__(self):
-        return (self.__class__, (list(self),),
-                getattr(self, '__dict__', None))
-
-    def add(self, item):
-        self.data.add(ref(item, self._remove))
-
-    def clear(self):
-        self.data.clear()
-
-    def copy(self):
-        return self.__class__(self)
-
-    def pop(self):
-        while True:
-            itemref = self.data.pop()
-            item = itemref()
-            if item is not None:
-                return item
-
-    def remove(self, item):
-        self.data.remove(ref(item))
-
-    def discard(self, item):
-        self.data.discard(ref(item))
-
-    def update(self, other):
-        if isinstance(other, self.__class__):
-            self.data.update(other.data)
-        else:
-            for element in other:
-                self.add(element)
-    __ior__ = update
-
-    # Helper functions for simple delegating methods.
-    def _apply(self, other, method):
-        if not isinstance(other, self.__class__):
-            other = self.__class__(other)
-        newdata = method(other.data)
-        newset = self.__class__()
-        newset.data = newdata
-        return newset
-
-    def _apply_mutate(self, other, method):
-        if not isinstance(other, self.__class__):
-            other = self.__class__(other)
-        method(other)
-
-    def difference(self, other):
-        return self._apply(other, self.data.difference)
-    __sub__ = difference
-
-    def difference_update(self, other):
-        self._apply_mutate(self, self.data.difference_update)
-    __isub__ = difference_update
-
-    def intersection(self, other):
-        return self._apply(other, self.data.intersection)
-    __and__ = intersection
-
-    def intersection_update(self, other):
-        self._apply_mutate(self, self.data.intersection_update)
-    __iand__ = intersection_update
-
-    def issubset(self, other):
-        return self.data.issubset(ref(item) for item in other)
-    __lt__ = issubset
-
-    def issuperset(self, other):
-        return self.data.issuperset(ref(item) for item in other)
-    __gt__ = issuperset
-
-    def symmetric_difference(self, other):
-        return self._apply(other, self.data.symmetric_difference)
-    __xor__ = symmetric_difference
-
-    def symmetric_difference_update(self, other):
-        self._apply_mutate(other, self.data.symmetric_difference_update)
-    __ixor__ = symmetric_difference_update
-
-    def union(self, other):
-        self._apply_mutate(other, self.data.union)
-    __or__ = union