diff --git a/underscore.js b/underscore.js
index bb4ea3bfd..f28f46ff1 100644
--- a/underscore.js
+++ b/underscore.js
@@ -670,6 +670,9 @@
   // underscore functions. Wrapped objects may be chained.
   var wrapper = function(obj) { this._wrapped = obj; };
 
+  // Expose `wrapper.prototype` as `_.prototype`
+  _.prototype = wrapper.prototype;
+
   // Helper function to continue chaining intermediate results.
   var result = function(obj, chain) {
     return chain ? _(obj).chain() : obj;