diff --git a/js/amount.js b/js/amount.js
index d791e8c9..b0ac9c0e 100644
--- a/js/amount.js
+++ b/js/amount.js
@@ -193,7 +193,7 @@ Amount.prototype.copyTo = function(d, negate) {
   if ('object' === typeof this.value)
   {
     if (this.is_native && negate)
-      this.value.negate.copyTo(d.value);
+      this.value.negate().copyTo(d.value);
     else
       this.value.copyTo(d.value);
   }
@@ -204,7 +204,7 @@ Amount.prototype.copyTo = function(d, negate) {
 
   d.offset	= this.offset;
   d.is_native	= this.is_native;
-  d.is_negative	= this.is_negative ? undefined : !this.is_negative;
+  d.is_negative	= this.is_native ? undefined : !this.is_negative;
 
   this.currency.copyTo(d.currency);
   this.issuer.copyTo(d.issuer);
diff --git a/test/amount-test.js b/test/amount-test.js
index 9b10dad5..97654d2a 100644
--- a/test/amount-test.js
+++ b/test/amount-test.js
@@ -1,55 +1,71 @@
 var buster  = require("buster");
 
 var amount  = require("../js/amount.js");
+var Amount  = require("../js/amount.js").Amount;
+var UInt160  = require("../js/amount.js").UInt160;
 
 buster.testCase("Amount", {
   "UInt160" : {
     "Parse 0" : function () {
-      buster.assert.equals(0, amount.UInt160.from_json("0").value);
+      buster.assert.equals(0, UInt160.from_json("0").value);
     },
     "Parse 0 export" : function () {
-      buster.assert.equals(amount.consts.hex_xns, amount.UInt160.from_json("0").to_json());
+      buster.assert.equals(amount.consts.hex_xns, UInt160.from_json("0").to_json());
     },
   },
-  "Amount" : {
+  "Amount parsing" : {
     "Parse native 0" : function () {
-      buster.assert.equals("0/XNS", amount.Amount.from_json("0").to_text_full());
+      buster.assert.equals("0/XNS", Amount.from_json("0").to_text_full());
     },
     "Parse native 0.0" : function () {
-      buster.assert.equals("0/XNS", amount.Amount.from_json("0.0").to_text_full());
+      buster.assert.equals("0/XNS", Amount.from_json("0.0").to_text_full());
     },
     "Parse native -0" : function () {
-      buster.assert.equals("0/XNS", amount.Amount.from_json("-0").to_text_full());
+      buster.assert.equals("0/XNS", Amount.from_json("-0").to_text_full());
     },
     "Parse native -0.0" : function () {
-      buster.assert.equals("0/XNS", amount.Amount.from_json("-0.0").to_text_full());
+      buster.assert.equals("0/XNS", Amount.from_json("-0.0").to_text_full());
     },
     "Parse native 1000" : function () {
-      buster.assert.equals("1000/XNS", amount.Amount.from_json("1000").to_text_full());
+      buster.assert.equals("1000/XNS", Amount.from_json("1000").to_text_full());
     },
     "Parse native 12.3" : function () {
-      buster.assert.equals("12300000/XNS", amount.Amount.from_json("12.3").to_text_full());
+      buster.assert.equals("12300000/XNS", Amount.from_json("12.3").to_text_full());
     },
     "Parse native -12.3" : function () {
-      buster.assert.equals("-12300000/XNS", amount.Amount.from_json("-12.3").to_text_full());
+      buster.assert.equals("-12300000/XNS", Amount.from_json("-12.3").to_text_full());
     },
     "Parse 123./USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("123./USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("123./USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
     },
     "Parse 12300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("12300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("12300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("12300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("12300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
     },
     "Parse 12.3/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("12.3/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("12.3/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("12.3/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("12.3/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
     },
     "Parse 1.2300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("1.23/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("1.2300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("1.23/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("1.2300/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
     },
     "Parse -0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("-0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("-0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
     },
     "Parse -0.0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh" : function () {
-      buster.assert.equals("0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", amount.Amount.from_json("-0.0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+      buster.assert.equals("0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("-0.0/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").to_text_full());
+    },
+  },
+  "Amount operations" : {
+    "Negate native 123" : function () {
+      buster.assert.equals("-123/XNS", Amount.from_json("123").negate().to_text_full());
+    },
+    "Negate native -123" : function () {
+      buster.assert.equals("123/XNS", Amount.from_json("-123").negate().to_text_full());
+    },
+    "Negate non-native 123" : function () {
+      buster.assert.equals("-123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").negate().to_text_full());
+    },
+    "Negate non-native -123" : function () {
+      buster.assert.equals("123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh", Amount.from_json("-123/USD/rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh").negate().to_text_full());
     },
   }
 });