diff --git a/spec/core/EnvSpec.js b/spec/core/EnvSpec.js
index 935f48d0..61c52511 100644
--- a/spec/core/EnvSpec.js
+++ b/spec/core/EnvSpec.js
@@ -82,8 +82,8 @@ describe("Env", function() {
   describe('#it', function () {
     it('throws an error when it receives a non-fn argument', function() {
       expect(function() {
-        env.it('undefined arg', undefined);
-      }).toThrowError(/it expects a function argument; received \[object (Undefined|DOMWindow|Object)\]/);
+        env.it('undefined arg', null);
+      }).toThrowError(/it expects a function argument; received \[object (Null|DOMWindow|Object)\]/);
     });
 
     it('does not throw when it is not given a fn argument', function() {
@@ -105,8 +105,8 @@ describe("Env", function() {
 
     it('throws an error when it receives a non-fn argument', function() {
       expect(function() {
-        env.xit('undefined arg', undefined);
-      }).toThrowError(/xit expects a function argument; received \[object (Undefined|DOMWindow|Object)\]/);
+        env.xit('undefined arg', null);
+      }).toThrowError(/xit expects a function argument; received \[object (Null|DOMWindow|Object)\]/);
     });
 
     it('does not throw when it is not given a fn argument', function() {
diff --git a/src/core/Env.js b/src/core/Env.js
index 0f4198e1..f5877d92 100644
--- a/src/core/Env.js
+++ b/src/core/Env.js
@@ -452,7 +452,7 @@ getJasmineRequireObj().Env = function(j$) {
     this.it = function(description, fn, timeout) {
       // it() sometimes doesn't have a fn argument, so only check the type if
       // it's given.
-      if (arguments.length > 1) {
+      if (arguments.length > 1 && typeof fn !== 'undefined') {
         ensureIsFunction(fn, 'it');
       }
       var spec = specFactory(description, fn, currentDeclarationSuite, timeout);
@@ -466,7 +466,7 @@ getJasmineRequireObj().Env = function(j$) {
     this.xit = function(description, fn, timeout) {
       // xit(), like it(), doesn't always have a fn argument, so only check the
       // type when needed.
-      if (arguments.length > 1) {
+      if (arguments.length > 1 && typeof fn !== 'undefined') {
         ensureIsFunction(fn, 'xit');
       }
       var spec = this.it.apply(this, arguments);