diff --git a/lib/system/windows/index.js b/lib/system/windows/index.js
index <HASH>..<HASH> 100644
--- a/lib/system/windows/index.js
+++ b/lib/system/windows/index.js
@@ -24,8 +24,9 @@ var clean_string = function(str){
 

 exports.process_running = function(process_name, callback){

   var cmd = 'tasklist /fi "imagename eq ' + process_name + '"';

-  exec(cmd, function(err, stdout){

-    callback(stdout && stdout.toString().indexOf(process_name) !== -1);

+  exec(cmd, function(err, stdout) {

+    var bool = stdout && stdout.toString().indexOf(process_name) !== -1;

+    callback(!!bool);

   });

 };
Make sure process_running in Windows returns a bool.