diff --git a/tcl/Util.tcl b/tcl/Util.tcl
index baf21f34..c796f055 100644
--- a/tcl/Util.tcl
+++ b/tcl/Util.tcl
@@ -433,7 +433,7 @@ proc sta_unknown { args } {
 	  "ambiguous command name \"$name\": [lsort $cmds]"
       }
     } else {
-      return [uplevel 1 builtin_unknown $args]
+      return [uplevel 1 [builtin_unknown $args]]
     }
   }
 }