diff --git a/index.js b/index.js
index fbd6c9b0..98fc7ffa 100644
--- a/index.js
+++ b/index.js
@@ -3,7 +3,9 @@
 const { MODULE_VERSION } = require('./lib/schemapack.js');
 
 const _ = require('lodash'),
-  SchemaPack = require('./lib/schemapack.js').SchemaPack;
+  SchemaPack = require('./lib/schemapack.js').SchemaPack,
+  UserError = require('./lib/common/UserError'),
+  DEFAULT_INVALID_ERROR = 'Provided definition is invalid';
 
 module.exports = {
   // Old API wrapping the new API
@@ -13,7 +15,7 @@ module.exports = {
     if (schema.validated) {
       return schema.convert(cb);
     }
-    return cb(null, schema.validationResult);
+    return cb(new UserError(_.get(schema, 'validationResult.reason', DEFAULT_INVALID_ERROR)));
   },
 
   convertV2: function(input, options, cb) {
@@ -23,7 +25,7 @@ module.exports = {
       return schema.convertV2(cb);
     }
 
-    return cb(null, schema.validationResult);
+    return cb(new UserError(_.get(schema, 'validationResult.reason', DEFAULT_INVALID_ERROR)));
   },
 
   validate: function (input) {
diff --git a/test/unit/base.test.js b/test/unit/base.test.js
index 1e7e9090..991c0384 100644
--- a/test/unit/base.test.js
+++ b/test/unit/base.test.js
@@ -993,19 +993,19 @@ describe('CONVERT FUNCTION TESTS ', function() {
       });
     });
 
-    it('should not return undefined in the error message if spec is not valid JSON/YAML', function(done) {
+    it('should return correct error message if spec is not valid JSON/YAML', function(done) {
       // invalid JSON
-      Converter.convert({ type: 'string', data: '{"key": { "value" : } ' }, {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.be.false;
-        expect(conversionResult.reason).to.not.include('undefined');
+      Converter.convert({ type: 'string', data: '{"key": { "value" : } ' }, {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message).to.include('Invalid format. Input must be in YAML or JSON format.');
       });
 
       // invalid YAML
-      Converter.convert({ type: 'string', data: ' :' }, {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.be.false;
-        expect(conversionResult.reason).to.not.include('undefined');
+      Converter.convert({ type: 'string', data: ' :' }, {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message).to.include('Invalid format. Input must be in YAML or JSON format.');
         done();
       });
     });
@@ -1013,10 +1013,10 @@ describe('CONVERT FUNCTION TESTS ', function() {
     it('should throw an invalid format error and not semantic version missing error when yaml.safeLoad ' +
     'does not throw an error while parsing yaml', function(done) {
       // YAML for which yaml.safeLoad does not throw an error
-      Converter.convert({ type: 'string', data: 'no error yaml' }, {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.be.false;
-        expect(conversionResult.reason).to.not.include('Specification must contain a semantic version number' +
+      Converter.convert({ type: 'string', data: 'no error yaml' }, {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message).to.not.include('Specification must contain a semantic version number' +
         ' of the OAS specification');
         done();
       });
@@ -1349,10 +1349,10 @@ describe('CONVERT FUNCTION TESTS ', function() {
     it('The converter must throw an error for invalid null info', function (done) {
       var openapi = fs.readFileSync(invalidNullInfo, 'utf8');
       Converter.convert({ type: 'string', data: openapi },
-        {}, (err, conversionResult) => {
-          expect(err).to.be.null;
-          expect(conversionResult.result).to.equal(false);
-          expect(conversionResult.reason)
+        {}, (err) => {
+          expect(err).to.not.be.null;
+          expect(err.name).to.eql('UserError');
+          expect(err.message)
             .to.equal('Specification must contain an Info Object for the meta-data of the API');
           done();
         });
@@ -1361,10 +1361,10 @@ describe('CONVERT FUNCTION TESTS ', function() {
     it('The converter must throw an error for invalid null info title', function (done) {
       var openapi = fs.readFileSync(invalidNullInfoTitle, 'utf8');
       Converter.convert({ type: 'string', data: openapi },
-        {}, (err, conversionResult) => {
-          expect(err).to.be.null;
-          expect(conversionResult.result).to.equal(false);
-          expect(conversionResult.reason)
+        {}, (err) => {
+          expect(err).to.not.be.null;
+          expect(err.name).to.eql('UserError');
+          expect(err.message)
             .to.equal('Specification must contain a title in order to generate a collection');
           done();
         });
@@ -1373,10 +1373,10 @@ describe('CONVERT FUNCTION TESTS ', function() {
     it('The converter must throw an error for invalid null info version', function (done) {
       var openapi = fs.readFileSync(invalidNullInfoVersion, 'utf8');
       Converter.convert({ type: 'string', data: openapi },
-        {}, (err, conversionResult) => {
-          expect(err).to.be.null;
-          expect(conversionResult.result).to.equal(false);
-          expect(conversionResult.reason)
+        {}, (err) => {
+          expect(err).to.not.be.null;
+          expect(err.name).to.eql('UserError');
+          expect(err.message)
             .to.equal('Specification must contain a semantic version number of the API in the Info Object');
           done();
         });
@@ -2408,9 +2408,9 @@ describe('INTERFACE FUNCTION TESTS ', function () {
           validationResult = Converter.validate({ type: 'string', data: openapi });
 
         expect(validationResult.result).to.equal(false);
-        Converter.convert({ type: 'string', data: openapi }, {}, function(err, conversionResult) {
-          expect(err).to.be.null;
-          expect(conversionResult.result).to.equal(false);
+        Converter.convert({ type: 'string', data: openapi }, {}, function(err) {
+          expect(err).to.not.be.null;
+          expect(err.name).to.eql('UserError');
           done();
         });
       });
@@ -2422,9 +2422,10 @@ describe('INTERFACE FUNCTION TESTS ', function () {
       var result = Converter.validate({ type: 'fil', data: 'invalid_path' });
       expect(result.result).to.equal(false);
       expect(result.reason).to.contain('input');
-      Converter.convert({ type: 'fil', data: 'invalid_path' }, {}, function(err, conversionResult) {
-        expect(conversionResult.result).to.equal(false);
-        expect(conversionResult.reason).to.equal('Invalid input type (fil). type must be one of file/json/string.');
+      Converter.convert({ type: 'fil', data: 'invalid_path' }, {}, function(err) {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message).to.equal('Invalid input type (fil). type must be one of file/json/string.');
         done();
       });
     });
@@ -2434,9 +2435,10 @@ describe('INTERFACE FUNCTION TESTS ', function () {
     it('(type: file)', function(done) {
       var result = Converter.validate({ type: 'file', data: 'invalid_path' });
       expect(result.result).to.equal(false);
-      Converter.convert({ type: 'file', data: 'invalid_path' }, {}, function(err, result) {
-        expect(result.result).to.equal(false);
-        expect(result.reason).to.equal('ENOENT: no such file or directory, open \'invalid_path\'');
+      Converter.convert({ type: 'file', data: 'invalid_path' }, {}, function(err) {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message).to.equal('ENOENT: no such file or directory, open \'invalid_path\'');
         done();
       });
     });
diff --git a/test/unit/bin.test.js b/test/unit/bin.test.js
index b5f2cef5..2996b7c0 100644
--- a/test/unit/bin.test.js
+++ b/test/unit/bin.test.js
@@ -33,10 +33,11 @@ describe('openapi2postmanv2 ', function() {
   });
 
   it('should show appropriate messages for invalid input', function (done) {
-    exec('./bin/openapi2postmanv2.js -s test/data/invalid_openapi/multiple-components.yaml', function(err, stdout) {
-      expect(err).to.be.null;
-      expect(stdout).to.include('duplicated mapping key');
-      done();
-    });
+    exec('./bin/openapi2postmanv2.js -s test/data/invalid_openapi/multiple-components.yaml',
+      function(err, stdout, stderr) {
+        expect(err).to.be.null;
+        expect(stderr).to.include('duplicated mapping key');
+        done();
+      });
   });
 });
diff --git a/test/unit/convertV2.test.js b/test/unit/convertV2.test.js
index 194f9903..85c9d99f 100644
--- a/test/unit/convertV2.test.js
+++ b/test/unit/convertV2.test.js
@@ -947,19 +947,19 @@ describe('The convert v2 Function', function() {
     });
   });
 
-  it('should not return undefined in the error message if spec is not valid JSON/YAML', function(done) {
+  it('should return correct error message if spec is not valid JSON/YAML', function(done) {
     // invalid JSON
-    Converter.convertV2({ type: 'string', data: '{"key": { "value" : } ' }, {}, (err, conversionResult) => {
-      expect(err).to.be.null;
-      expect(conversionResult.result).to.be.false;
-      expect(conversionResult.reason).to.not.include('undefined');
+    Converter.convertV2({ type: 'string', data: '{"key": { "value" : } ' }, {}, (err) => {
+      expect(err).to.not.be.null;
+      expect(err.name).to.eql('UserError');
+      expect(err.message).to.include('Invalid format. Input must be in YAML or JSON format.');
     });
 
     // invalid YAML
-    Converter.convertV2({ type: 'string', data: ' :' }, {}, (err, conversionResult) => {
-      expect(err).to.be.null;
-      expect(conversionResult.result).to.be.false;
-      expect(conversionResult.reason).to.not.include('undefined');
+    Converter.convertV2({ type: 'string', data: ' :' }, {}, (err) => {
+      expect(err).to.not.be.null;
+      expect(err.name).to.eql('UserError');
+      expect(err.message).to.include('Invalid format. Input must be in YAML or JSON format.');
       done();
     });
   });
@@ -967,10 +967,10 @@ describe('The convert v2 Function', function() {
   it('should throw an invalid format error and not semantic version missing error when yaml.safeLoad ' +
   'does not throw an error while parsing yaml', function(done) {
     // YAML for which yaml.safeLoad does not throw an error
-    Converter.convertV2({ type: 'string', data: 'no error yaml' }, {}, (err, conversionResult) => {
-      expect(err).to.be.null;
-      expect(conversionResult.result).to.be.false;
-      expect(conversionResult.reason).to.not.include('Specification must contain a semantic version number' +
+    Converter.convertV2({ type: 'string', data: 'no error yaml' }, {}, (err) => {
+      expect(err).to.not.be.null;
+      expect(err.name).to.eql('UserError');
+      expect(err.message).to.not.include('Specification must contain a semantic version number' +
       ' of the OAS specification');
       done();
     });
@@ -1244,10 +1244,10 @@ describe('The convert v2 Function', function() {
   it('The converter must throw an error for invalid null info', function (done) {
     var openapi = fs.readFileSync(invalidNullInfo, 'utf8');
     Converter.convertV2({ type: 'string', data: openapi },
-      {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.equal(false);
-        expect(conversionResult.reason)
+      {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message)
           .to.equal('Specification must contain an Info Object for the meta-data of the API');
         done();
       });
@@ -1256,10 +1256,10 @@ describe('The convert v2 Function', function() {
   it('The converter must throw an error for invalid null info title', function (done) {
     var openapi = fs.readFileSync(invalidNullInfoTitle, 'utf8');
     Converter.convertV2({ type: 'string', data: openapi },
-      {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.equal(false);
-        expect(conversionResult.reason)
+      {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message)
           .to.equal('Specification must contain a title in order to generate a collection');
         done();
       });
@@ -1268,10 +1268,10 @@ describe('The convert v2 Function', function() {
   it('The converter must throw an error for invalid null info version', function (done) {
     var openapi = fs.readFileSync(invalidNullInfoVersion, 'utf8');
     Converter.convertV2({ type: 'string', data: openapi },
-      {}, (err, conversionResult) => {
-        expect(err).to.be.null;
-        expect(conversionResult.result).to.equal(false);
-        expect(conversionResult.reason)
+      {}, (err) => {
+        expect(err).to.not.be.null;
+        expect(err.name).to.eql('UserError');
+        expect(err.message)
           .to.equal('Specification must contain a semantic version number of the API in the Info Object');
         done();
       });