diff --git a/Demo/classes/Complex.py b/Demo/classes/Complex.py
index a779897..2019cdf 100755
--- a/Demo/classes/Complex.py
+++ b/Demo/classes/Complex.py
@@ -165,7 +165,7 @@
         other = ToComplex(other)
         return cmp(other, self)
 
-    def __nonzero__(self):
+    def __bool__(self):
         return not (self.re == self.im == 0)
 
     abs = radius = __abs__
diff --git a/Demo/classes/Rat.py b/Demo/classes/Rat.py
index 55543b6..24670b6 100755
--- a/Demo/classes/Rat.py
+++ b/Demo/classes/Rat.py
@@ -223,7 +223,7 @@
         return cmp(Rat(a), b)
 
     # a != 0
-    def __nonzero__(a):
+    def __bool__(a):
         return a.__num != 0
 
     # coercion