diff --git a/src/ajax.js b/src/ajax.js
index 790585dd..e6c9ac8a 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -15,7 +15,10 @@ var r20 = /%20/g,
 	rselectTextarea = /^(?:select|textarea)/i,
 	rspacesAjax = /\s+/,
 	rts = /([?&])_=[^&]*/,
-	rucWord = /(^|\-)([a-z])/g,
+	rucHeaders = /(^|\-)([a-z])/g,
+	rucHeadersFunc = function( _, $1, $2 ) {
+		return $1 + $2.toUpperCase();
+	},
 	rurl = /^([\w\+\.\-]+:)\/\/([^\/?#:]*)(?::(\d+))?/,
 
 	// Keep a copy of the old load method
@@ -402,9 +405,7 @@ jQuery.extend({
 				// Caches the header
 				setRequestHeader: function( name, value ) {
 					if ( !state ) {
-						requestHeaders[ name.toLowerCase().replace( rucWord, function( _, $1, $2 ) {
-							return $1 + $2.toUpperCase();
-						} ) ] = value;
+						requestHeaders[ name.toLowerCase().replace( rucHeaders, rucHeadersFunc ) ] = value;
 					}
 					return this;
 				},