diff --git a/lib/matchers/number.js b/lib/matchers/number.js
index 3f5f15f..1824bfa 100644
--- a/lib/matchers/number.js
+++ b/lib/matchers/number.js
@@ -1,4 +1,6 @@
-var s = require('../s');
+var s        = require('../s');
+var utils    = require('../utils');
+var hasValue = utils.hasValue;
 
 var parseFloatFromString = function (value) {
   if(/^(\-|\+)?([0-9]+(\.[0-9]+)?)$/.test(value))
@@ -7,9 +9,19 @@ var parseFloatFromString = function (value) {
 }
 
 module.exports = function (opts) {
-
   if (!opts) opts = {};
 
+  var hasMinValue = hasValue(opts.min);
+  var hasMaxValue = hasValue(opts.max);
+
+  if(hasMinValue && typeof opts.min !== 'number') {
+    throw new Error('Invalid minimum option: ' + opts.min);
+  }
+
+  if(hasMaxValue && typeof opts.max !== 'number') {
+    throw new Error('Invalid maximum option: ' + opts.max);
+  }
+
   return s(function(value) {
 
     if (opts.parse) {
@@ -21,13 +33,13 @@ module.exports = function (opts) {
     }
 
     if (opts) {
-      if (opts.min && opts.max && (value < opts.min || value > opts.max)) {
+      if (hasMinValue && hasMaxValue && (value < opts.min || value > opts.max)) {
         return 'should be a number between ' + opts.min + ' and ' + opts.max;
       }
-      if (opts.min && value < opts.min) {
+      if (hasMinValue && value < opts.min) {
         return 'should be a number >= ' + opts.min;
       }
-      if (opts.max && value > opts.max) {
+      if (hasMaxValue && value > opts.max) {
         return 'should be a number <= ' + opts.max;
       }
     }
diff --git a/lib/utils.js b/lib/utils.js
new file mode 100644
index 0000000..2cbd76f
--- /dev/null
+++ b/lib/utils.js
@@ -0,0 +1,7 @@
+var hasValue = function(val){
+  return (typeof val !== 'undefined') && (val !== null);
+}
+
+module.exports = {
+  hasValue: hasValue
+}
diff --git a/test/matchers/number.spec.js b/test/matchers/number.spec.js
index 1be0bc5..f49261e 100644
--- a/test/matchers/number.spec.js
+++ b/test/matchers/number.spec.js
@@ -16,10 +16,27 @@ describe('number matcher', function() {
 
   it('supports min and max', function() {
     number({min: 3})('', 0).should.have.error(/should be a number >= 3/);
+    number({min: 0})('', -10).should.have.error(/should be a number >= 0/);
+    number({max: 0})('', 12).should.have.error(/should be a number <= 0/);
     number({max: 3})('', 5).should.have.error(/should be a number <= 3/);
     number({min: 3, max: 5})('', 7).should.have.error(/should be a number between 3 and 5/);
   });
 
+  it('fails for invalid min or max values', function(){
+    var shouldFail = function(val) {
+      (function(){
+        number({min: val});
+      }).should.throw('Invalid minimum option: ' + val);
+
+      (function(){
+        number({max: val});
+      }).should.throw('Invalid maximum option: ' + val);
+    }
+
+    var invalidValues = ['a', '', {}, []];
+    invalidValues.forEach(shouldFail);
+  });
+
   it('can parse string into number', function() {
     number({parse: true})('', 0).should.not.have.error();
     number({parse: true})('', 3).should.not.have.error();
diff --git a/test/util.spec.js b/test/util.spec.js
new file mode 100644
index 0000000..875e310
--- /dev/null
+++ b/test/util.spec.js
@@ -0,0 +1,28 @@
+var utils    = require('../lib/utils');
+var hasValue = utils.hasValue;
+
+describe("hasValue() util function", function(){
+  it('Should return false when value is <null>', function(){
+    hasValue(null).should.be.false;
+  });
+
+  it('Should return false when value is <undefined>', function(){
+    hasValue(undefined).should.be.false;
+  });
+
+  it('Should return true when value is a number', function(){
+    hasValue(12).should.be.true;
+  });
+
+  it('Should return true when value is a string', function(){
+    hasValue('a').should.be.true;
+  });
+
+  it('Should return true when value is <{}>', function(){
+    hasValue({}).should.be.true;
+  });
+
+  it('Should return true when value is <"">', function(){
+    hasValue('').should.be.true;
+  });
+});