diff --git a/lib/chai/core/assertions.js b/lib/chai/core/assertions.js
index 2b7988213..47a4e5ea6 100644
--- a/lib/chai/core/assertions.js
+++ b/lib/chai/core/assertions.js
@@ -211,13 +211,7 @@ module.exports = function (chai, _) {
     var obj = flag(this, 'object');
     var expected = false;
 
-    if (_.type(obj) !== 'array' && _.type(obj) !== 'string' && _.type(obj) !== 'object') {
-      this.assert(
-          false
-        , 'argument of expect() must be an array, an object, or a string, ' + _.type(obj) + ' given'
-        , 'argument of expect() must be an array, an object, or a string, ' + _.type(obj) + ' given');
-      return;
-    }
+    new Assertion(obj).to.be.a(['array', 'object', 'string']);
 
     if (_.type(obj) === 'array' && _.type(val) === 'object') {
       for (var i in obj) {
diff --git a/test/assert.js b/test/assert.js
index cee5daeab..562fd870d 100644
--- a/test/assert.js
+++ b/test/assert.js
@@ -440,17 +440,24 @@ describe('assert', function () {
 
     err(function () {
       assert.include(42, 'bar');
-    }, "argument of expect() must be an array, an object, or a string, number given");
+    }, "expected 42 to be an array, an object, or a string");
+
+    err(function(){
+      assert.include(null, 42);
+    }, "expected null to be an array, an object, or a string");
 
     err(function () {
       assert.include(undefined, 'bar');
-    }, "argument of expect() must be an array, an object, or a string, undefined given");
+    }, "expected undefined to be an array, an object, or a string");
   });
 
   it('notInclude', function () {
     assert.notInclude('foobar', 'baz');
     assert.notInclude([ 1, 2, 3 ], 4);
-    assert.notInclude(undefined, 'bar');
+
+    err(function () {
+      assert.notInclude(undefined, 'bar');
+    }, "expected undefined to be an array, an object, or a string");
 
     err(function () {
       assert.notInclude('foobar', 'bar');
diff --git a/test/expect.js b/test/expect.js
index e7c1171f3..fd2f32463 100644
--- a/test/expect.js
+++ b/test/expect.js
@@ -668,7 +668,15 @@ describe('expect', function () {
 
     err(function(){
       expect(42.0).to.include(42);
-    }, "argument of expect() must be an array, an object, or a string, number given");
+    }, "expected 42 to be an array, an object, or a string");
+
+    err(function(){
+      expect(null).to.not.include(42);
+    }, "expected null to be an array, an object, or a string");
+
+    err(function(){
+      expect(undefined).to.not.include(42);
+    }, "expected undefined to be an array, an object, or a string");
   });
 
   it('keys(array|Object|arguments)', function(){
diff --git a/test/should.js b/test/should.js
index 3fbbcf33e..ca0d49e48 100644
--- a/test/should.js
+++ b/test/should.js
@@ -503,7 +503,7 @@ describe('should', function() {
 
     err(function(){
       (42).should.include(4);
-    }, "argument of expect() must be an array, an object, or a string, number given");
+    }, "expected 42 to be an array, an object, or a string");
   });
 
   it('keys(array|Object|arguments)', function(){