#7624: Fix isinstance(foo(), collections.Callable) for old-style classes.
diff --git a/Lib/abc.py b/Lib/abc.py
index 8aeb2af..c37ed8f 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -4,6 +4,11 @@
"""Abstract Base Classes (ABCs) according to PEP 3119."""
+# Instance of old-style class
+class _C: pass
+_InstanceType = type(_C())
+
+
def abstractmethod(funcobj):
"""A decorator indicating abstract methods.
@@ -124,6 +129,9 @@
if subclass in cls._abc_cache:
return True
subtype = type(instance)
+ # Old-style instances
+ if subtype is _InstanceType:
+ subtype = subclass
if subtype is subclass or subclass is None:
if (cls._abc_negative_cache_version ==
ABCMeta._abc_invalidation_counter and