diff --git a/js/amount.js b/js/amount.js
index 07a578047..49a60c073 100644
--- a/js/amount.js
+++ b/js/amount.js
@@ -12,7 +12,7 @@ var UInt160 = function () {
   //   XXX Should standardize on 'i' format or 20 format.
 };
 
-UInt160.prototype.from_json = function (j) {
+UInt160.from_json = function (j) {
   var u	= new UInt160();
 
   return u.parse_json(j);
diff --git a/test/amount-test.js b/test/amount-test.js
new file mode 100644
index 000000000..3a7e656a7
--- /dev/null
+++ b/test/amount-test.js
@@ -0,0 +1,13 @@
+var buster  = require("buster");
+
+var amount  = require("../js/amount.js");
+
+buster.testCase("Amount", {
+  "UInt160" : {
+    "Parse 0" : function () {
+      buster.assert.equals(0, amount.UInt160.from_json("0").value);
+    },
+  }
+});
+
+// vim:sw=2:sts=2:ts=8