diff --git a/src/ajax.js b/src/ajax.js
index 568a75dce1..7c5c83888b 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -221,7 +221,7 @@ jQuery.extend({
 
 		// Build temporary JSONP function
 		if ( s.dataType === "json" && (s.data && jsre.test(s.data) || jsre.test(s.url)) ) {
-			jsonp = "jsonp" + jsc++;
+			jsonp = s.jsonpCallback || ("jsonp" + jsc++);
 
 			// Replace the =? sequence both in the query string and the data
 			if ( s.data ) {
@@ -235,7 +235,7 @@ jQuery.extend({
 			s.dataType = "script";
 
 			// Handle JSONP-style loading
-			window[ jsonp ] = function(tmp){
+			window[ jsonp ] = window[ jsonp ] || function(tmp){
 				data = tmp;
 				success();
 				complete();
diff --git a/test/unit/ajax.js b/test/unit/ajax.js
index d827a15300..4d63ce5a6d 100644
--- a/test/unit/ajax.js
+++ b/test/unit/ajax.js
@@ -518,10 +518,10 @@ test("jQuery.getScript(String, Function) - no callback", function() {
 });
 
 test("jQuery.ajax() - JSONP, Local", function() {
-	expect(7);
+	expect(8);
 
 	var count = 0;
-	function plus(){ if ( ++count == 7 ) start(); }
+	function plus(){ if ( ++count == 8 ) start(); }
 
 	stop();
 
@@ -579,6 +579,20 @@ test("jQuery.ajax() - JSONP, Local", function() {
 		}
 	});
 
+	jQuery.ajax({
+		url: "data/jsonp.php",
+		dataType: "jsonp",
+		jsonpCallback: "jsonpResults",
+		success: function(data){
+			ok( data.data, "JSON results returned (GET, custom callback name)" );
+			plus();
+		},
+		error: function(data){
+			ok( false, "Ajax error JSON (GET, custom callback name)" );
+			plus();
+		}
+	});
+
 	jQuery.ajax({
 		type: "POST",
 		url: "data/jsonp.php",
@@ -624,6 +638,22 @@ test("jQuery.ajax() - JSONP, Local", function() {
 	});
 });
 
+test("JSONP - Custom JSONP Callback", function() {
+	expect(1);
+	stop();
+
+	window.jsonpResults = function(data) {
+		ok( data.data, "JSON results returned (GET, custom callback function)" );
+		start();
+	};
+
+	jQuery.ajax({
+		url: "data/jsonp.php",
+		dataType: "jsonp",
+		jsonpCallback: "jsonpResults"
+	});
+});
+
 test("jQuery.ajax() - JSONP, Remote", function() {
 	expect(4);