diff --git a/src/css.js b/src/css.js
index 2eeef6cc..17ac136b 100644
--- a/src/css.js
+++ b/src/css.js
@@ -3,7 +3,8 @@
 var ralpha = /alpha\([^)]*\)/i,
 	ropacity = /opacity=([^)]*)/,
 	rdashAlpha = /-([a-z])/ig,
-	rupper = /([A-Z])/g,
+	// fixed for IE9, see #8346
+	rupper = /([A-Z]|^ms)/g,
 	rnumpx = /^-?\d+(?:px)?$/i,
 	rnum = /^-?\d/,