Index: Lib/inspect.py
===================================================================
--- Lib/inspect.py	(revision 75274)
+++ Lib/inspect.py	(working copy)
@@ -242,7 +242,7 @@
 
 def isabstract(object):
     """Return true if the object is an abstract base class (ABC)."""
-    return isinstance(object, type) and object.__flags__ & TPFLAGS_IS_ABSTRACT
+    return bool(isinstance(object, type) and object.__flags__ & TPFLAGS_IS_ABSTRACT)
 
 def getmembers(object, predicate=None):
     """Return all members of an object as (name, value) pairs sorted by name.
Index: Lib/test/test_inspect.py
===================================================================
--- Lib/test/test_inspect.py	(revision 75274)
+++ Lib/test/test_inspect.py	(working copy)
@@ -115,7 +115,37 @@
         self.assertTrue('a' in members)
         self.assertTrue('b' not in members)
 
+    def test_isabstract(self):
+        from abc import ABCMeta, abstractmethod
 
+        class AbstractClassExample(object):
+            __metaclass__ = ABCMeta
+
+            @abstractmethod
+            def foo(self):
+                pass
+
+        class ClassExample(AbstractClassExample):
+            def foo(self):
+                pass
+
+        a = ClassExample()
+
+        # Test general behaviour.
+        self.assertTrue(inspect.isabstract(AbstractClassExample))
+        self.assertFalse(inspect.isabstract(ClassExample))
+        self.assertFalse(inspect.isabstract(a))
+        self.assertFalse(inspect.isabstract(int))
+        self.assertFalse(inspect.isabstract(5))
+
+        # Test if function actually returns a boolean.
+        self.assertTrue(isinstance(inspect.isabstract(AbstractClassExample), bool))
+        self.assertTrue(isinstance(inspect.isabstract(ClassExample), bool))
+        self.assertTrue(isinstance(inspect.isabstract(a), bool))
+        self.assertTrue(isinstance(inspect.isabstract(int), bool))
+        self.assertTrue(isinstance(inspect.isabstract(5), bool))
+
+
 class TestInterpreterStack(IsTestBase):
     def __init__(self, *args, **kwargs):
         unittest.TestCase.__init__(self, *args, **kwargs)