diff --git a/src/js/amount.js b/src/js/amount.js
index be10b6f6..521aeaad 100644
--- a/src/js/amount.js
+++ b/src/js/amount.js
@@ -249,7 +249,7 @@ Currency.from_json = function (j) {
       : j.clone();
 };
 
-currency.is_valid = function (j) {
+Currency.is_valid = function (j) {
   return currency.from_json(j).is_valid();
 };
 
diff --git a/test/amount-test.js b/test/amount-test.js
index bbd19c8b..98eff5b0 100644
--- a/test/amount-test.js
+++ b/test/amount-test.js
@@ -38,6 +38,10 @@ buster.testCase("Amount", {
     "is_valid('rrrrrrrrrrrrrrrrrrrrrhoLvTp')" : function () {
       buster.assert(UInt160.is_valid("rrrrrrrrrrrrrrrrrrrrrhoLvTp"));
     },
+
+    "!is_valid('rrrrrrrrrrrrrrrrrrrrrhoLvT')" : function () {
+      buster.refute(UInt160.is_valid("rrrrrrrrrrrrrrrrrrrrrhoLvT"));
+    },
   },
 
   "Amount parsing" : {