diff --git a/lib/aruba/contracts/is_power_of_two.rb b/lib/aruba/contracts/is_power_of_two.rb
index adfd739e..6d0a449a 100644
--- a/lib/aruba/contracts/is_power_of_two.rb
+++ b/lib/aruba/contracts/is_power_of_two.rb
@@ -15,7 +15,7 @@ class IsPowerOfTwo
       def self.valid?(value)
         # explanation for algorithm can be found here:
         # http://www.exploringbinary.com/ten-ways-to-check-if-an-integer-is-a-power-of-two-in-c/
-        value.positive? && (value & (value - 1)).zero?
+        value.positive? && value.nobits?(value - 1)
       rescue StandardError
         false
       end