diff --git a/lib/chai/interface/assert.js b/lib/chai/interface/assert.js
index 82d26dc6d..a4f478b4d 100644
--- a/lib/chai/interface/assert.js
+++ b/lib/chai/interface/assert.js
@@ -1004,10 +1004,36 @@ module.exports = function (chai, util) {
    */
 
   assert.operator = function (val, operator, val2, msg) {
-    if (!~['==', '===', '>', '>=', '<', '<=', '!=', '!=='].indexOf(operator)) {
-      throw new Error('Invalid operator "' + operator + '"');
+    var ok;
+    switch(operator) {
+      case '==':
+        ok = val == val2;
+        break;
+      case '===':
+        ok = val === val2;
+        break;
+      case '>':
+        ok = val > val2;
+        break;
+      case '>=':
+        ok = val >= val2;
+        break;
+      case '<':
+        ok = val < val2;
+        break;
+      case '<=':
+        ok = val <= val2;
+        break;
+      case '!=':
+        ok = val != val2;
+        break;
+      case '!==':
+        ok = val !== val2;
+        break;
+      default:
+        throw new Error('Invalid operator "' + operator + '"');
     }
-    var test = new Assertion(eval(val + operator + val2), msg);
+    var test = new Assertion(ok, msg);
     test.assert(
         true === flag(test, 'object')
       , 'expected ' + util.inspect(val) + ' to be ' + operator + ' ' + util.inspect(val2)
diff --git a/test/assert.js b/test/assert.js
index 1445ccb35..6fe53e976 100644
--- a/test/assert.js
+++ b/test/assert.js
@@ -556,6 +556,9 @@ describe('assert', function () {
   });
 
   it('operator', function() {
+    // For testing undefined and null with == and ===
+    var w;
+    
     assert.operator(1, '<', 2);
     assert.operator(2, '>', 1);
     assert.operator(1, '==', 1);
@@ -563,6 +566,10 @@ describe('assert', function () {
     assert.operator(1, '>=', 1);
     assert.operator(1, '!=', 2);
     assert.operator(1, '!==', 2);
+    assert.operator(1, '!==', '1');
+    assert.operator(w, '==', undefined);
+    assert.operator(w, '===', undefined);
+    assert.operator(w, '==', null);
 
     err(function () {
       assert.operator(1, '=', 2);
@@ -579,6 +586,10 @@ describe('assert', function () {
     err(function () {
       assert.operator(1, '==', 2);
      }, "expected 1 to be == 2");
+     
+    err(function () {
+      assert.operator(1, '===', '1');
+     }, "expected 1 to be === \'1\'");
 
     err(function () {
       assert.operator(2, '<=', 1);
@@ -591,10 +602,16 @@ describe('assert', function () {
     err(function () {
       assert.operator(1, '!=', 1);
      }, "expected 1 to be != 1");
-
+     
+    err(function () {
+      assert.operator(1, '!==', 1);
+     }, "expected 1 to be !== 1");
+    
     err(function () {
-      assert.operator(1, '!==', '1');
-     }, "expected 1 to be !== \'1\'");
+      assert.operator(w, '===', null);
+     }, "expected undefined to be === null");
+     
+     
   });
 
   it('closeTo', function(){