diff --git a/lib/ip.js b/lib/ip.js
index f3480a6..5b5ccc2 100644
--- a/lib/ip.js
+++ b/lib/ip.js
@@ -201,7 +201,7 @@ ip.subnet = function (addr, mask) {
     }
   }
 
-  var numberOfAddresses = 2 ** (32 - maskLength);
+  var numberOfAddresses = Math.pow(2, 32 - maskLength);
 
   return {
     networkAddress: ip.fromLong(networkAddress),