diff --git a/src/node.js b/src/node.js
index 1e091d0289..c8f55c6b07 100644
--- a/src/node.js
+++ b/src/node.js
@@ -137,7 +137,7 @@ process.mixin = function() {
 					, copy );
 
 				// Don't bring in undefined values
-				else if ( copy !== undefined )
+				else
 					target[ name ] = copy;
 
 			}
diff --git a/test/mjsunit/test-process-mixin.js b/test/mjsunit/test-process-mixin.js
index 840079a35d..f3578251a2 100644
--- a/test/mjsunit/test-process-mixin.js
+++ b/test/mjsunit/test-process-mixin.js
@@ -13,4 +13,10 @@ var fakeDomElement = {deep: {nodeType: 4}};
 target = {};
 process.mixin(true, target, fakeDomElement);
 
-assert.notStrictEqual(target.deep, fakeDomElement.deep);
\ No newline at end of file
+assert.notStrictEqual(target.deep, fakeDomElement.deep);
+
+var objectWithUndefinedValue = {foo: undefined};
+target = {};
+
+process.mixin(target, objectWithUndefinedValue);
+assert.ok(target.hasOwnProperty('foo'));
\ No newline at end of file