diff --git a/lib/contract.js b/lib/contract.js
index d17a36f53..8cc00cc90 100644
--- a/lib/contract.js
+++ b/lib/contract.js
@@ -44,14 +44,28 @@ function zpad(buffer, length) {
     return buffer;
 }
 
+// There seems to be a but in maskn, so we are doing this for now.
+var bitmasks = [];
+(function() {
+    var mask = '';
+    for (var i = 0; i < 33; i++) {
+        bitmasks.push(new utils.BN(mask, 16));
+        mask += 'ff';
+    }
+})();
+
 function coderNumber(size, signed) {
     return {
         encode: function(value) {
             value = numberOrBN(value)
+            value = value.toTwos(size * 8).and(bitmasks[size]);
             if (signed) {
-                value = value.toTwos(32 * 8);
-            } else if (value < 0) {
-                value = value.toTwos(size * 8);
+                value = value.fromTwos(size * 8).toTwos(256);
+                //value = value.toTwos(size * 8).and(bitmasks[size]).fromTwos(size * 8).toTwos(256);
+//            } else { //if (value.isNeg()) {
+//                value = value.toTwos(size * 8).and(bitmasks[size]);
+//            } else {
+//                value = value.and(bitmasks[size]);
             }
             return value.toArrayLike(Buffer, 'be', 32);
         },
@@ -60,7 +74,7 @@ function coderNumber(size, signed) {
             if (signed) {
                 value = value.fromTwos(size * 8);
             } else {
-                value = value.mod((new utils.BN(2)).pow(new utils.BN(size * 8)))
+                value = value.fromTwos(size * 8); //.toTwos(256); //mod((new utils.BN(2)).pow(new utils.BN(size * 8)))
             }
             return {
                 consumed: 32,