diff --git a/Lib/ast.py b/Lib/ast.py
index 4c8c7795ff8..03b8a1b16b7 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -346,7 +346,10 @@ def __instancecheck__(cls, inst):
             except AttributeError:
                 return False
             else:
-                return isinstance(value, _const_types[cls])
+                return (
+                    isinstance(value, _const_types[cls]) and
+                    not isinstance(value, _const_types_not.get(cls, ()))
+                )
         return type.__instancecheck__(cls, inst)
 
 def _new(cls, *args, **kwargs):
@@ -384,3 +387,6 @@ def __new__(cls, *args, **kwargs):
     NameConstant: (type(None), bool),
     Ellipsis: (type(...),),
 }
+_const_types_not = {
+    Num: (bool,),
+}
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index 897e705a42c..4bf77ff046e 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -411,12 +411,16 @@ def test_isinstance(self):
         self.assertFalse(isinstance(ast.Str('42'), ast.Bytes))
         self.assertFalse(isinstance(ast.Num(42), ast.NameConstant))
         self.assertFalse(isinstance(ast.Num(42), ast.Ellipsis))
+        self.assertFalse(isinstance(ast.NameConstant(True), ast.Num))
+        self.assertFalse(isinstance(ast.NameConstant(False), ast.Num))
 
         self.assertFalse(isinstance(ast.Constant('42'), ast.Num))
         self.assertFalse(isinstance(ast.Constant(42), ast.Str))
         self.assertFalse(isinstance(ast.Constant('42'), ast.Bytes))
         self.assertFalse(isinstance(ast.Constant(42), ast.NameConstant))
         self.assertFalse(isinstance(ast.Constant(42), ast.Ellipsis))
+        self.assertFalse(isinstance(ast.Constant(True), ast.Num))
+        self.assertFalse(isinstance(ast.Constant(False), ast.Num))
 
         self.assertFalse(isinstance(ast.Constant(), ast.Num))
         self.assertFalse(isinstance(ast.Constant(), ast.Str))
diff --git a/Misc/NEWS.d/next/Library/2019-01-13-18-42-41.bpo-35733.eFfLiv.rst b/Misc/NEWS.d/next/Library/2019-01-13-18-42-41.bpo-35733.eFfLiv.rst
new file mode 100644
index 00000000000..8e5ef9b8417
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-01-13-18-42-41.bpo-35733.eFfLiv.rst
@@ -0,0 +1,2 @@
+``ast.Constant(boolean)`` no longer an instance of :class:`ast.Num`.  Patch by Anthony
+Sottile.