diff --git a/lib/transaction/output.js b/lib/transaction/output.js
index b5493c6..66385fc 100644
--- a/lib/transaction/output.js
+++ b/lib/transaction/output.js
@@ -7,6 +7,7 @@ var bufferUtil = require('../util/buffer');
 var JSUtil = require('../util/js');
 var BufferWriter = require('../encoding/bufferwriter');
 var Script = require('../script');
+var $ = require('../util/preconditions');
 
 function Output(params) {
   if (!(this instanceof Output)) {
@@ -50,6 +51,10 @@ Object.defineProperty(Output.prototype, 'satoshis', {
       this._satoshisBN = BN.fromNumber(num);
       this._satoshis = num;
     }
+    $.checkState(
+      JSUtil.isPositiveInteger(this._satoshis),
+      'Output satoshis is not a positive integer'
+    );
   }
 });
 
diff --git a/test/transaction/output.js b/test/transaction/output.js
index 93a35c1..fdade46 100644
--- a/test/transaction/output.js
+++ b/test/transaction/output.js
@@ -30,6 +30,52 @@ describe('Output', function() {
     newOutput.satoshis.should.equal(100);
   });
 
+  it('can be assigned a satoshi amount with a string', function() {
+    var newOutput = new Output({
+      satoshis: '100',
+      script: Script.empty()
+    });
+    newOutput.satoshis.should.equal(100);
+  });
+
+  describe('will error if output is not a positive integer', function() {
+    it('-100', function() {
+      (function() {
+        var newOutput = new Output({
+          satoshis: -100,
+          script: Script.empty()
+        });
+      }).should.throw('Output satoshis is not a positive integer');
+    });
+
+    it('1.1', function() {
+      (function() {
+        var newOutput = new Output({
+          satoshis: 1.1,
+          script: Script.empty()
+        });
+      }).should.throw('Output satoshis is not a positive integer');
+    });
+
+    it('NaN', function() {
+      (function() {
+        var newOutput = new Output({
+          satoshis: NaN,
+          script: Script.empty()
+        });
+      }).should.throw('Output satoshis is not a positive integer');
+    });
+
+    it('Infinity', function() {
+      (function() {
+        var newOutput = new Output({
+          satoshis: Infinity,
+          script: Script.empty()
+        });
+      }).should.throw('Output satoshis is not a positive integer');
+    });
+  });
+
   var expectEqualOutputs = function(a, b) {
     a.satoshis.should.equal(b.satoshis);
     a.script.toString().should.equal(b.script.toString());