diff --git a/bin/lessc b/bin/lessc
index 733f0eff..02be342f 100755
--- a/bin/lessc
+++ b/bin/lessc
@@ -16,7 +16,7 @@ var options = {
 args = args.filter(function (arg) {
     var match;
 
-    if (match = arg.match(/^--?([a-z][a-z-]*)$/i)) { arg = match[1] }
+    if (match = arg.match(/^--?([a-z][0-9a-z-]*)$/i)) { arg = match[1] }
     else { return arg }
 
     switch (arg) {