diff --git a/src/xhr.js b/src/xhr.js
index 57903e04..4896e6cb 100644
--- a/src/xhr.js
+++ b/src/xhr.js
@@ -87,7 +87,7 @@ jQuery.xhr = function( _native ) {
 		}
 		
 		// Apply option prefilters
-		for (i in prefilters) {
+		for ( i = 0; i < prefilters.length; i++ ) {
 			prefilters[i](s);
 		}