diff --git a/lib/jobManager.js b/lib/jobManager.js
index 3b704e0..5a27be9 100644
--- a/lib/jobManager.js
+++ b/lib/jobManager.js
@@ -86,13 +86,13 @@ var JobManager = module.exports = function JobManager(options){
     var diffDividend = (function(){
         switch(options.algorithm){
             case 'sha256':
-                return 0x00000000ffff0000000000000000000000000000000000000000000000000000;
+                return '00000000ffff0000000000000000000000000000000000000000000000000000';
             case 'scrypt':
             case 'scrypt-jane':
-                return 0x0000ffff00000000000000000000000000000000000000000000000000000000;
+                return '0000ffff00000000000000000000000000000000000000000000000000000000';
             case 'quark':
             case 'x11':
-                return 0x000000ffff000000000000000000000000000000000000000000000000000000;
+                return '000000ffff000000000000000000000000000000000000000000000000000000';
         }
     })();
 
@@ -214,7 +214,7 @@ var JobManager = module.exports = function JobManager(options){
             blockHash = util.reverseBuffer(util.doublesha(headerBuffer)).toString('hex');
         }
         else {
-            var targetUser = bignum(diffDividend / difficulty);
+            var targetUser = bignum(diffDividend, 16).div(difficulty);
             if (headerBigNum.gt(targetUser)){
                 return shareError([23, 'low difficulty share']);
             }
@@ -245,4 +245,4 @@ var JobManager = module.exports = function JobManager(options){
         return {result: true, error: null, solution: blockHash};
     };
 };
-JobManager.prototype.__proto__ = events.EventEmitter.prototype;
\ No newline at end of file
+JobManager.prototype.__proto__ = events.EventEmitter.prototype;