diff --git a/lib/model/txproposal.js b/lib/model/txproposal.js
index 8f4378d..112a48a 100644
--- a/lib/model/txproposal.js
+++ b/lib/model/txproposal.js
@@ -13,26 +13,36 @@ function TxProposal() {
 };
 
 TxProposal.TYPE_SIMPLE = 'simple';
-TxProposal.TYPE_MULTIPLEOUTPUTS = 'multiple-outputs';
+TxProposal.TYPE_MULTIPLEOUTPUTS = 'multiple_outputs';
 
-TxProposal.prototype._createSimple = function(opts) {
-  this.toAddress = opts.toAddress;
-  this.amount = opts.amount;
-  this.outputOrder = _.shuffle(_.range(2));
-  this.network = Bitcore.Address(this.toAddress).toObject().network;
+TxProposal.prototype._isTypeSupported = function() {
+  var supported = [TxProposal.TYPE_SIMPLE, TxProposal.TYPE_MULTIPLEOUTPUTS];
+  return !this.type || supported.indexOf(this.type) > -1;
 };
 
-TxProposal.prototype._createMultipleOutputs = function(opts) {
-  this.outputs = opts.outputs;
-  this.outputOrder = _.shuffle(_.range(this.outputs.length + 1));
-  this.network = Bitcore.Address(this.outputs[0].toAddress).toObject().network;
+TxProposal._create = {};
+
+TxProposal._create.simple = function(txp, opts) {
+  txp.toAddress = opts.toAddress;
+  txp.amount = opts.amount;
+  txp.outputOrder = _.shuffle(_.range(2));
+  txp.network = Bitcore.Address(txp.toAddress).toObject().network;
+};
+
+TxProposal._create.multiple_outputs = function(txp, opts) {
+  txp.outputs = opts.outputs;
+  txp.outputOrder = _.shuffle(_.range(txp.outputs.length + 1));
+  txp.network = Bitcore.Address(txp.outputs[0].toAddress).toObject().network;
 };
 
 TxProposal.create = function(opts) {
   opts = opts || {};
 
   var x = new TxProposal();
-  x.type = opts.type;
+  x.type = opts.type || TxProposal.TYPE_SIMPLE;
+  if (!x._isTypeSupported()) {
+    throw new Error('Unsupported transaction proposal type');
+  };
 
   var now = Date.now();
   x.createdOn = Math.floor(now / 1000);
@@ -52,11 +62,7 @@ TxProposal.create = function(opts) {
   x.fee = null;
   x.feePerKb = opts.feePerKb;
 
-  if (x.type == TxProposal.TYPE_MULTIPLEOUTPUTS) {
-    x._createMultipleOutputs(opts);
-  } else {
-    x._createSimple(opts);
-  }
+  TxProposal._create[x.type](x, opts);
 
   return x;
 };
@@ -64,8 +70,12 @@ TxProposal.create = function(opts) {
 TxProposal.fromObj = function(obj) {
   var x = new TxProposal();
 
+  x.type = obj.type || TxProposal.TYPE_SIMPLE;
+  if (!x._isTypeSupported()) {
+    throw new Error('Unsupported transaction proposal type');
+  };
+
   x.version = obj.version;
-  x.type = obj.type;
   x.createdOn = obj.createdOn;
   x.id = obj.id;
   x.walletId = obj.walletId;
diff --git a/test/models/txproposal.js b/test/models/txproposal.js
index 6180486..77d213d 100644
--- a/test/models/txproposal.js
+++ b/test/models/txproposal.js
@@ -6,19 +6,53 @@ var sinon = require('sinon');
 var should = chai.should();
 var TXP = require('../../lib/model/txproposal');
 var Bitcore = require('bitcore-wallet-utils').Bitcore;
-var multiple_outputs = TXP.TYPE_MULTIPLEOUTPUTS;
 
 
 describe('TXProposal', function() {
 
-  describe('#fromObj', function() {
+  describe('#create', function() {
     it('should create a TXP', function() {
-      var txp = TXP.fromObj(aTXP());
+      var txp = TXP.create(aTxpOpts());
       should.exist(txp);
+      should.exist(txp.toAddress);
+      should.not.exist(txp.outputs);
     });
     it('should create a multiple-outputs TXP', function() {
-      var txp = TXP.fromObj(aTXP(multiple_outputs));
+      var txp = TXP.create(aTxpOpts(TXP.TYPE_MULTIPLEOUTPUTS));
+      should.exist(txp);
+      should.not.exist(txp.toAddress);
+      should.exist(txp.outputs);
+    });
+    it('should fail to create a TXP of unknown type', function() {
+      var txp;
+      try {
+        txp = TXP.create(aTxpOpts('bogus'));
+      } catch(e) {
+        should.exist(e);
+      }
+      should.not.exist(txp);
+    });
+  });
+
+  describe('#fromObj', function() {
+    it('should copy a TXP', function() {
+      var txp = TXP.fromObj(aTXP());
+      should.exist(txp);
+      txp.toAddress.should.equal(aTXP().toAddress);
+    });
+    it('should copy a multiple-outputs TXP', function() {
+      var txp = TXP.fromObj(aTXP(TXP.TYPE_MULTIPLEOUTPUTS));
       should.exist(txp);
+      txp.outputs.should.deep.equal(aTXP(TXP.TYPE_MULTIPLEOUTPUTS).outputs);
+    });
+    it('should fail to copy a TXP of unknown type', function() {
+      var txp;
+      try {
+        txp = TXP.fromObj(aTxpOpts('bogus'));
+      } catch(e) {
+        should.exist(e);
+      }
+      should.not.exist(txp);
     });
   });
 
@@ -40,7 +74,7 @@ describe('TXProposal', function() {
       t.getChangeOutput().should.deep.equal(t.outputs[0]);
     });
     it('should create a bitcore TX with multiple outputs', function() {
-      var txp = TXP.fromObj(aTXP(multiple_outputs));
+      var txp = TXP.fromObj(aTXP(TXP.TYPE_MULTIPLEOUTPUTS));
       txp.outputOrder = [0, 1, 2];
       var t = txp.getBitcoreTx();
       t.getChangeOutput().should.deep.equal(t.outputs[2]);
@@ -98,9 +132,36 @@ var theXPriv = 'xprv9s21ZrQH143K2rMHbXTJmWTuFx6ssqn1vyRoZqPkCXYchBSkp5ey8kMJe84s
 var theXPub = 'xpub661MyMwAqRbcFLRkhYzK8eQdoywNHJVsJCMQNDoMks5bZymuMcyDgYfnVQYq2Q9npnVmdTAthYGc3N3uxm5sEdnTpSqBc4YYTAhNnoSxCm9';
 var theSignatures = ['3045022100896aeb8db75fec22fddb5facf791927a996eb3aee23ee6deaa15471ea46047de02204c0c33f42a9d3ff93d62738712a8c8a5ecd21b45393fdd144e7b01b5a186f1f9'];
 
+var aTxpOpts = function(type) {
+  var opts = {
+    type: type,
+    toAddress: '18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7',
+    amount: 50000000,
+    message: 'some message'
+  };
+  if (type == TXP.TYPE_MULTIPLEOUTPUTS) {
+    opts.outputs = [
+      {
+        toAddress: "18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7",
+        amount: 10000000,
+        message: "first message"
+      },
+      {
+        toAddress: "18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7",
+        amount: 20000000,
+        message: "second message"
+      },
+    ];
+    delete opts.toAddress;
+    delete opts.amount;
+  }
+  return opts;
+};
+
 var aTXP = function(type) {
   var txp = {
     "version": "1.0.0",
+    "type": type,
     "createdOn": 1423146231,
     "id": "75c34f49-1ed6-255f-e9fd-0c71ae75ed1e",
     "walletId": "1",
@@ -136,8 +197,7 @@ var aTXP = function(type) {
     "actions": [],
     "outputOrder": [0, 1],
   };
-  if (type == 'multiple-outputs') {
-    txp.type = type;
+  if (type == TXP.TYPE_MULTIPLEOUTPUTS) {
     txp.outputs = [
       {
         toAddress: "18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7",