diff --git a/.gitignore b/.gitignore
index 2be4b24..375322f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,8 +4,6 @@ node_modules
 browser/tests.js
 docs/api
 
-lib/errors/index.js
-
 CONTRIBUTING.html
 LICENSE.html
 README.html
diff --git a/gulpfile.js b/gulpfile.js
index ed80a78..012a2b8 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -21,7 +21,6 @@
  * <li> `browser:compressed` - build `browser/bitcore.min.js`
  * <li> `browser:maketests` - build `browser/tests.js`, needed for testing without karma
  * </ul>`
- * <li> `errors` - autogenerate the `./lib/errors/index.js` file with error definitions
  * <li> `lint` - run `jshint`
  * <li> `coverage` - run `istanbul` with mocha to generate a report of test coverage
  * <li> `jsdoc` - run `jsdoc` to generate the API reference
@@ -73,9 +72,9 @@ var testKarma = shell.task([
  * Testing
  */
 
-gulp.task('test:node', ['errors'], testMocha);
+gulp.task('test:node', testMocha);
 
-gulp.task('test:node:nofail', ['errors'], function() {
+gulp.task('test:node:nofail', function() {
   return testMocha().on('error', ignoreError);
 });
 
@@ -93,7 +92,7 @@ gulp.task('browser:makefolder', shell.task([
   'if [ ! -d "browser" ]; then mkdir browser; fi'
 ]));
 
-gulp.task('browser:uncompressed', ['browser:makefolder', 'errors'], shell.task([
+gulp.task('browser:uncompressed', ['browser:makefolder'], shell.task([
   './node_modules/.bin/browserify index.js --insert-global-vars=true --standalone=bitcore -o browser/bitcore.js'
 ]));
 
@@ -116,11 +115,6 @@ gulp.task('browser', function(callback) {
   runSequence(['browser:compressed'], ['browser:maketests'], callback);
 });
 
-gulp.task('errors', shell.task([
-  'node ./lib/errors/build.js'
-]));
-
-
 /**
  * Code quality and documentation
  */
diff --git a/lib/errors/build.js b/lib/errors/build.js
deleted file mode 100644
index 723e1e4..0000000
--- a/lib/errors/build.js
+++ /dev/null
@@ -1,49 +0,0 @@
-'use strict';
-
-var _ = require('lodash');
-var fs = require('fs');
-
-var defineElement = function(fullName, baseClass, message) {
-  return fullName + ' = function() {\n' +
-         '  this.message = ' + message + ';\n' +
-         '  this.stack = this.message + \'\\n\' + (new Error()).stack;\n' +
-         '};\n' +
-         fullName + '.prototype = Object.create(' + baseClass + '.prototype);\n' +
-         fullName + '.prototype.name = "' + fullName + '";\n\n';
-};
-
-var traverseNode = function(baseClass, errorDefinition) {
-  var className = baseClass + '.' + errorDefinition.name;
-  var generated = defineElement(className, baseClass, errorDefinition.message);
-  if (errorDefinition.errors) {
-    generated += childDefinitions(className, errorDefinition.errors);
-  }
-  return generated;
-};
-
-/* jshint latedef: false */
-var childDefinitions = function(parent, childDefinitions) {
-  var generated = '';
-  _.each(childDefinitions, function(childDefinition) {
-    generated += traverseNode(parent, childDefinition);
-  });
-  return generated;
-};
-/* jshint latedef: true */
-
-var traverseRoot = function(errorsDefinition) {
-  var fullName = 'bitcore.Error';
-  var path = 'Error';
-  var generated = '\'use strict\';\n\n';
-  generated += '/* jshint maxlen: 300 */\n';
-  generated += '/* jshint quotmark: false */\n';
-  generated += '/* AUTOGENERATED FILE. DON\'T EDIT, MODIFY "lib/errors/spec.js" INSTEAD */\n\n';
-  generated += 'var bitcore = {};\n\n';
-  generated += defineElement(fullName, path, '\'Internal error\'');
-  generated += childDefinitions(fullName, errorsDefinition);
-  generated += 'module.exports = bitcore.Error;\n';
-  return generated;
-};
-
-var data = require('./spec');
-fs.writeFileSync(__dirname + '/index.js', traverseRoot(data));
diff --git a/lib/errors/index.js b/lib/errors/index.js
new file mode 100644
index 0000000..921b2ff
--- /dev/null
+++ b/lib/errors/index.js
@@ -0,0 +1,60 @@
+'use strict';
+
+var _ = require('lodash');
+
+function format(message, args) {
+  return message
+    .replace('{0}', args[0])
+    .replace('{1}', args[1])
+    .replace('{2}', args[2]);
+}
+var traverseNode = function(parent, errorDefinition) {
+  var NodeError = function() {
+    if (_.isString(errorDefinition.message)) {
+      this.message = format(errorDefinition.message, arguments);
+    } else if (_.isFunction(errorDefinition.message)) {
+      this.message = errorDefinition.message.apply(null, arguments);
+    } else {
+      throw new Error('Invalid error definition for ' + errorDefinition.name);
+    }
+    this.stack = this.message + '\n' + (new Error()).stack;
+  };
+  NodeError.prototype = Object.create(parent.prototype);
+  NodeError.prototype.name = parent.prototype.name + errorDefinition.name;
+  parent[errorDefinition.name] = NodeError;
+  if (errorDefinition.errors) {
+    childDefinitions(NodeError, errorDefinition.errors);
+  }
+};
+
+/* jshint latedef: false */
+var childDefinitions = function(parent, childDefinitions) {
+  _.each(childDefinitions, function(childDefinition) {
+    traverseNode(parent, childDefinition);
+  });
+};
+/* jshint latedef: true */
+
+var traverseRoot = function(parent, errorsDefinition) {
+  childDefinitions(parent, errorsDefinition);
+  return parent;
+};
+
+
+var bitcore = {};
+bitcore.Error = function() {
+  this.message = 'Internal error';
+  this.stack = this.message + '\n' + (new Error()).stack;
+};
+bitcore.Error.prototype = Object.create(Error.prototype);
+bitcore.Error.prototype.name = 'bitcore.Error';
+
+
+var data = require('./spec');
+traverseRoot(bitcore.Error, data);
+
+module.exports = bitcore.Error;
+
+module.exports.extend = function(spec) {
+  traverseRoot(bitcore.Error, spec);
+};
diff --git a/lib/errors/spec.js b/lib/errors/spec.js
index 70fbeac..c68150f 100644
--- a/lib/errors/spec.js
+++ b/lib/errors/spec.js
@@ -1,131 +1,125 @@
 'use strict';
 
-function format(arg) {
-  return '\'' + arg
-    .replace('{0}', '\' + arguments[0] + \'')
-    .replace('{1}', '\' + arguments[1] + \'')
-    .replace('{2}', '\' + arguments[2] + \'') + '\'';
-}
-
 module.exports = [{
-    name: 'InvalidB58Char',
-    message: format('Invalid Base58 character: {0} in {1}')
-  }, {
-    name: 'InvalidB58Checksum',
-    message: format('Invalid Base58 checksum for {0}')
-  }, {
-    name: 'InvalidNetwork',
-    message: format('Invalid version for network: got {0}')
+  name: 'InvalidB58Char',
+  message: 'Invalid Base58 character: {0} in {1}'
+}, {
+  name: 'InvalidB58Checksum',
+  message: 'Invalid Base58 checksum for {0}'
+}, {
+  name: 'InvalidNetwork',
+  message: 'Invalid version for network: got {0}'
+}, {
+  name: 'InvalidState',
+  message: 'Invalid state: {0}'
+}, {
+  name: 'NotImplemented',
+  message: 'Function {0} was not implemented yet'
+}, {
+  name: 'InvalidNetworkArgument',
+  message: 'Invalid network: must be "livenet" or "testnet", got {0}'
+}, {
+  name: 'InvalidArgument',
+  message: function() {
+    return 'Invalid Argument' + (arguments[0] ? (': ' + arguments[0]) : '');
+  }
+}, {
+  name: 'AbstractMethodInvoked',
+  message: 'Abstract Method Invokation: {0}'
+}, {
+  name: 'InvalidArgumentType',
+  message: function() {
+    return 'Invalid Argument for ' + arguments[2] + ', expected ' + arguments[1] + ' but got ' + typeof arguments[0];
+  }
+}, {
+  name: 'Unit',
+  message: 'Internal Error on Unit {0}',
+  errors: [{
+    'name': 'UnknownCode',
+    'message': 'Unrecognized unit code: {0}'
   }, {
-    name: 'InvalidState',
-    message: format('Invalid state: {0}')
+    'name': 'InvalidRate',
+    'message': 'Invalid exchange rate: {0}'
+  }]
+}, {
+  name: 'Transaction',
+  message: 'Internal Error on Transaction {0}',
+  errors: [{
+    name: 'Input',
+    message: 'Internal Error on Input {0}',
+    errors: [{
+      name: 'MissingScript',
+      message: 'Need a script to create an input'
+    }]
   }, {
-    name: 'NotImplemented',
-    message: format('Function {0} was not implemented yet')
+    name: 'NeedMoreInfo',
+    message: '{0}'
   }, {
-    name: 'InvalidNetworkArgument',
-    message: format('Invalid network: must be "livenet" or "testnet", got {0}')
+    name: 'UnableToVerifySignature',
+    message: 'Unable to verify signature: {0}'
   }, {
-    name: 'InvalidArgument',
-    message: format('Invalid Argument' + '\' + (arguments[0] ? \': {0}\' : \'\') + \'')
+    name: 'DustOutputs',
+    message: 'Dust amount detected in one output'
   }, {
-    name: 'AbstractMethodInvoked',
-    message: format('Abstract Method Invokation: {0}')
+    name: 'FeeError',
+    message: 'Fees are not correctly set {0}',
   }, {
-    name: 'InvalidArgumentType',
-    message: format('Invalid Argument for {2}, expected {1} but got ') + '+ typeof arguments[0]',
+    name: 'ChangeAddressMissing',
+    message: 'Change address is missing'
+  }]
+}, {
+  name: 'Script',
+  message: 'Internal Error on Script {0}',
+  errors: [{
+    name: 'UnrecognizedAddress',
+    message: 'Expected argument {0} to be an address'
+  }]
+}, {
+  name: 'HDPrivateKey',
+  message: 'Internal Error on HDPrivateKey {0}',
+  errors: [{
+    name: 'InvalidDerivationArgument',
+    message: 'Invalid derivation argument {0}, expected string, or number and boolean'
   }, {
-    name: 'Unit',
-    message: format('Internal Error on Unit {0}'),
+    name: 'InvalidEntropyArgument',
+    message: 'Invalid entropy: must be an hexa string or binary buffer, got {0}',
     errors: [{
-      'name': 'UnknownCode',
-      'message': format('Unrecognized unit code: {0}')
-    },{
-      'name': 'InvalidRate',
-      'message': format('Invalid exchange rate: {0}')
+      name: 'TooMuchEntropy',
+      message: 'Invalid entropy: more than 512 bits is non standard, got "{0}"'
+    }, {
+      name: 'NotEnoughEntropy',
+      message: 'Invalid entropy: at least 128 bits needed, got "{0}"'
     }]
   }, {
-    name: 'Transaction',
-    message: format('Internal Error on Transaction {0}'),
-    errors: [
-      {
-        name: 'Input',
-        message: format('Internal Error on Input {0}'),
-        errors: [{
-          name: 'MissingScript',
-          message: format('Need a script to create an input')
-        }]
-      }, {
-        name: 'NeedMoreInfo',
-        message: format('{0}')
-      }, {
-        name: 'UnableToVerifySignature',
-        message: format('Unable to verify signature: {0}')
-      }, {
-        name: 'DustOutputs',
-        message: format('Dust amount detected in one output')
-      }, {
-        name: 'FeeError',
-        message: format('Fees are not correctly set {0}'),
-      }, {
-        name: 'ChangeAddressMissing',
-        message: format('Change address is missing')
-      }
-    ]
+    name: 'InvalidLength',
+    message: 'Invalid length for xprivkey string in {0}'
   }, {
-    name: 'Script',
-    message: format('Internal Error on Script {0}'),
-    errors: [{
-      name: 'UnrecognizedAddress',
-      message: format('Expected argument {0} to be an address')
-    }]
+    name: 'InvalidPath',
+    message: 'Invalid derivation path: {0}'
   }, {
-    name: 'HDPrivateKey',
-    message: format('Internal Error on HDPrivateKey {0}'),
-    errors: [{
-      name: 'InvalidDerivationArgument',
-      message: format('Invalid derivation argument {0}, expected string, or number and boolean')
-    }, {
-      name: 'InvalidEntropyArgument',
-      message: format('Invalid entropy: must be an hexa string or binary buffer, got {0}'),
-      errors: [{
-        name: 'TooMuchEntropy',
-        message: format('Invalid entropy: more than 512 bits is non standard, got "{0}"')
-      }, {
-        name: 'NotEnoughEntropy',
-        message: format('Invalid entropy: at least 128 bits needed, got "{0}"')
-      }]
-    }, {
-      name: 'InvalidLength',
-      message: format('Invalid length for xprivkey string in {0}')
-    }, {
-      name: 'InvalidPath',
-      message: format('Invalid derivation path: {0}')
-    }, {
-      name: 'UnrecognizedArgument',
-      message: format('Invalid argument: creating a HDPrivateKey requires a string, buffer, json or object, got "{0}"')
-    }]
+    name: 'UnrecognizedArgument',
+    message: 'Invalid argument: creating a HDPrivateKey requires a string, buffer, json or object, got "{0}"'
+  }]
+}, {
+  name: 'HDPublicKey',
+  message: 'Internal Error on HDPublicKey {0}',
+  errors: [{
+    name: 'ArgumentIsPrivateExtended',
+    message: 'Argument is an extended private key: {0}'
   }, {
-    name: 'HDPublicKey',
-    message: format('Internal Error on HDPublicKey {0}'),
-    errors: [{
-      name: 'ArgumentIsPrivateExtended',
-      message: format('Argument is an extended private key: {0}')
-    }, {
-      name: 'InvalidDerivationArgument',
-      message: format('Invalid derivation argument: got {0}')
-    }, {
-      name: 'InvalidLength',
-      message: format('Invalid length for xpubkey: got "{0}"')
-    }, {
-      name: 'InvalidPath',
-      message: format('Invalid derivation path, it should look like: "m/1/100", got "{0}"')
-    }, {
-      name: 'MustSupplyArgument',
-      message: format('Must supply an argument to create a HDPublicKey')
-    }, {
-      name: 'UnrecognizedArgument',
-      message: format('Invalid argument for creation, must be string, json, buffer, or object')
-    }]
-  }
-];
+    name: 'InvalidDerivationArgument',
+    message: 'Invalid derivation argument: got {0}'
+  }, {
+    name: 'InvalidLength',
+    message: 'Invalid length for xpubkey: got "{0}"'
+  }, {
+    name: 'InvalidPath',
+    message: 'Invalid derivation path, it should look like: "m/1/100", got "{0}"'
+  }, {
+    name: 'MustSupplyArgument',
+    message: 'Must supply an argument to create a HDPublicKey'
+  }, {
+    name: 'UnrecognizedArgument',
+    message: 'Invalid argument for creation, must be string, json, buffer, or object'
+  }]
+}];