diff --git a/src/fx.js b/src/fx.js
index 15fce5c3a..fa1707294 100644
--- a/src/fx.js
+++ b/src/fx.js
@@ -219,7 +219,7 @@ jQuery.each({
 jQuery.extend({
 
 	speed: function(speed, easing, fn) {
-		var opt = typeof speed === "object" ? speed : {
+		var opt = speed && typeof speed === "object" ? speed : {
 			complete: fn || !fn && easing ||
 				jQuery.isFunction( speed ) && speed,
 			duration: speed,