diff --git a/src/selector.js b/src/selector.js
index abe7562f0..9cc75fc0e 100644
--- a/src/selector.js
+++ b/src/selector.js
@@ -246,7 +246,7 @@ var Expr = Sizzle.selectors = {
 		ID: /#((?:[\w\u0128-\uFFFF_-]|\\.)+)/,
 		CLASS: /\.((?:[\w\u0128-\uFFFF_-]|\\.)+)/,
 		NAME: /\[name=['"]*((?:[\w\u0128-\uFFFF_-]|\\.)+)['"]*\]/,
-		ATTR: /\[((?:[\w\u0128-\uFFFF_-]|\\.)+)\s*(?:(\S{0,1}=)\s*(['"]*)(.*?)\3|)\]/,
+		ATTR: /\[((?:[\w\u0128-\uFFFF_-]|\\.)+)\s*(?:(\S?=)\s*(['"]*)(.*?)\3|)\]/,
 		TAG: /^((?:[\w\u0128-\uFFFF\*_-]|\\.)+)/,
 		CHILD: /:(only|nth|last|first)-child\(?(even|odd|[\dn+-]*)\)?/,
 		POS: /:(nth|eq|gt|lt|first|last|even|odd)\(?(\d*)\)?(?:[^-]|$)/,