parentheses appear to be needed here for less

readable/bootswatch.less

@@ -60,7 +60,7 @@
   }
 }
 
-@media (max-width: @grid-float-breakpoint - 1) {
+@media (max-width: (@grid-float-breakpoint - 1)) {
   .navbar {
     .navbar-nav > li > a {
       margin: 0;