diff --git a/src/effects.js b/src/effects.js
index 51ce0c577..067383bc4 100644
--- a/src/effects.js
+++ b/src/effects.js
@@ -2,7 +2,7 @@
 
 var elemdisplay = {},
 	rfxtypes = /^(?:toggle|show|hide)$/,
-	rfxnum = /^([+\-]=)?([\d+.\-]+)(.*)$/,
+	rfxnum = /^([+\-]=)?([\d+.\-]+)([a-z%]*)$/i,
 	timerId,
 	fxAttrs = [
 		// height animations