src/Pure/General/cache.scala

     if (x == null) null
     else if (x == "") ""
     else if (x == "true") "true"
     else if (x == "false") "false"
     else if (x == "0.0") "0.0"
+    else if (Symbol.is_static_spaces(x)) Symbol.spaces(x.length)
     else if (Library.is_small_int(x)) Library.signed_string_of_int(Integer.parseInt(x))
     else {
       lookup(x) match {
         case Some(y) => y
         case None =>