diff --git a/lib/less/parser.js b/lib/less/parser.js
index d24bfc2f..efe41062 100644
--- a/lib/less/parser.js
+++ b/lib/less/parser.js
@@ -334,13 +334,14 @@ less.parser = {
             var attr = '', key, val, op;
 
             if (! $('[')) return;
-            if ((key = $(this.tag)) &&
-                (op = $(/[|~*$^]?=/g)) &&
-                (val = $(this.entities.string) || $(/[a-zA-Z0-9_-]+/g))) {
-                attr = [key, op, val].join('');
-            } else if (val = $(this.tag) || $(this.entities.string)) {
-                attr = val;
+
+            if (key = $(/[a-z]+/g) || $(this.entities.string)) {
+                if ((op = $(/[|~*$^]?=/g)) &&
+                    (val = $(this.entities.string) || $(/[\w-]+/g))) {
+                    attr = [key, op, val].join('');
+                } else { attr = key }
             }
+
             if (! $(']')) return;
 
             if (attr) { return "[" + attr + "]" }