diff --git a/lib/validations.js b/lib/validations.js
index 3455edf7..41f919b8 100644
--- a/lib/validations.js
+++ b/lib/validations.js
@@ -287,7 +287,7 @@ function validateLength(attr, conf, err, options) {
 function validateNumericality(attr, conf, err, options) {
   if (nullCheck.call(this, attr, conf, err)) return;
 
-  if (typeof this[attr] !== 'number') {
+  if (typeof this[attr] !== 'number' || isNaN(this[attr])) {
     return err('number');
   }
   if (conf.int && this[attr] !== Math.round(this[attr])) {
@@ -633,16 +633,26 @@ var defaultMessages = {
   uniqueness: 'is not unique',
 };
 
+/**
+ * Checks if attribute is undefined or null. Calls err function with 'blank' or 'null'.
+ * See defaultMessages. You can affect this behaviour with conf.allowBlank and conf.allowNull.
+ * @param {String} attr Property name of attribute
+ * @param {Object} conf conf object for validator
+ * @param {Function} err
+ * @return {Boolean} returns true if attribute is null or blank
+ */
 function nullCheck(attr, conf, err) {
-  if (this[attr] == null) {
-    if (!conf.allowNull) {
-      err('null');
+  // First determine if attribute is defined
+  if (typeof this[attr] === 'undefined') {
+    if (!conf.allowBlank) {
+      err('blank');
     }
     return true;
   } else {
-    if (blank(this[attr])) {
-      if (!conf.allowBlank) {
-        err('blank');
+    // Now check if attribute is null
+    if (this[attr] === null) {
+      if (!conf.allowNull) {
+        err('null');
       }
       return true;
     }
diff --git a/test/validations.test.js b/test/validations.test.js
index daed9985..fd79f613 100644
--- a/test/validations.test.js
+++ b/test/validations.test.js
@@ -558,7 +558,65 @@ describe('validations', function() {
   });
 
   describe('numericality', function() {
-    it('should validate numericality');
+    it('passes when given numeric values', function() {
+      User.validatesNumericalityOf('age');
+      var user = new User({age: 10});
+      user.isValid().should.be.true();
+    });
+
+    it('fails when given non-numeric values', function() {
+      User.validatesNumericalityOf('age');
+      var user = new User({age: 'notanumber'});
+      user.isValid().should.be.false();
+      user.errors.should.eql({age: ['is not a number']});
+    });
+
+    it('fails when given undefined values', function() {
+      User.validatesNumericalityOf('age');
+      var u = new User({});
+      u.isValid().should.be.false();
+      u.errors.should.eql({age: ['is blank']});
+    });
+
+    it('skips undefined values when allowBlank option is true', function() {
+      User.validatesNumericalityOf('age', {allowBlank: true});
+      var user = new User({});
+      user.isValid().should.be.true();
+    });
+
+    it('fails when given non-numeric values when allowBlank option is true', function() {
+      User.validatesNumericalityOf('age', {allowBlank: true});
+      var user = new User({age: 'test'});
+      user.isValid().should.be.false();
+      user.errors.should.eql({age: ['is not a number']});
+
+    });
+
+    it('fails when given null values', function() {
+      User.validatesNumericalityOf('age');
+      var user = new User({age: null});
+      user.isValid().should.be.false();
+      user.errors.should.eql({age: ['is null']});
+    });
+
+    it('passes when given null values when allowNull option is true', function() {
+      User.validatesNumericalityOf('age', {allowNull: true});
+      var user = new User({age: null});
+      user.isValid().should.be.true();
+    });
+
+    it('passes when given float values', function() {
+      User.validatesNumericalityOf('age');
+      var user = new User({age: 13.37});
+      user.isValid().should.be.true();
+    });
+
+    it('fails when given non-integer values when int option is true', function() {
+      User.validatesNumericalityOf('age', {int: true});
+      var user = new User({age: 13.37});
+      user.isValid().should.be.false();
+      user.errors.should.eql({age: ['is not an integer']});
+    });
   });
 
   describe('inclusion', function() {