diff --git a/src/core.js b/src/core.js
index 3859caa01..96a68c2e6 100644
--- a/src/core.js
+++ b/src/core.js
@@ -417,32 +417,22 @@ jQuery.extend({
 	},
 
 	isPlainObject: function( obj ) {
-		// Must be an Object.
-		// Because of IE, we also have to check the presence of the constructor property.
-		// Make sure that DOM nodes and window objects don't pass through, as well
-		if ( !obj || jQuery.type(obj) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
+		// Not plain objects: params that are not [[Class]] "[object Object]", DOM nodes, window
+		if ( jQuery.type( obj ) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
 			return false;
 		}
 
+		// Firefox 17+ will throw on host objects. ie window.location
 		try {
-			// Not own constructor property must be Object
 			if ( obj.constructor &&
-				!core_hasOwn.call(obj, "constructor") &&
-				!core_hasOwn.call(obj.constructor.prototype, "isPrototypeOf") ) {
+					!core_hasOwn.call( obj.constructor.prototype, "isPrototypeOf" ) ) {
 				return false;
 			}
 		} catch ( e ) {
-			// IE8,9 Will throw exceptions on certain host objects #9897
 			return false;
 		}
 
-		// Own properties are enumerated firstly, so to speed up,
-		// if last one is own, then all properties are own.
-
-		var key;
-		for ( key in obj ) {}
-
-		return key === undefined || core_hasOwn.call( obj, key );
+		return obj === Object( obj );
 	},
 
 	isEmptyObject: function( obj ) {