LW6 - non-toplevel interface containing capi:editor-pane without an echo area

After evaluating the following on LW6,


(capi:define-interface foo ()
   ()
   (:panes (a bar)))

(capi:define-interface bar ()
   ()
   (:panes
     (output capi:editor-pane
             :echo-area nil)))

(capi:contain (make-instance 'foo))


....activating a command which prompts the user (e.g., Control-s) raises 
a pop-up echo area, which is followed by a no-applicable-method error:

No applicable methods for #<STANDARD-GENERIC-FUNCTION 
CAPI-LIBRARY:REPRESENTATION-INTERFACE-GEOMETRY 311A5C4A> with args (NIL)

CL-USER 1 : 1 > :b
Call to ERROR
Call to CERROR
Call to (METHOD NO-APPLICABLE-METHOD (T))
Call to CAPI::UPDATE-STANDARD-EDITOR-FLOATER
Call to (METHOD CAPI::RAISE-STANDARD-FLOATING-EDITOR (CAPI:EDITOR-PANE))
Call to (METHOD CAPI::RAISE-FLOATING-ECHO-AREA (CAPI:EDITOR-PANE))
Call to CLOS::NEXT-METHOD-CALL-2
Call to CLOS::METHOD-COMBINATION-TEMPLATE
Call to CLOS::NEXT-METHOD-CALL-2
Call to (METHOD EDITOR:FIND-ECHO-AREA-WINDOW :AROUND (T T))
Call to CLOS::METHOD-COMBINATION-TEMPLATE
Call to EDITOR::CHECK-ECHO-AREA
Call to EDITOR::CURRENT-ECHO-AREA-BUFFER
Call to EDITOR::CURRENT-PARSING-INFORMATION
Call to EDITOR::PROMPTING
Call to EDITOR::INCREMENTAL-SEARCH-SOMEHOW
Call to (SUBFUNCTION EDITOR::FUNCTION-MAYBE-INHIBITED 
EDITOR::FUNCALL-COMMAND-FUNCTION)
Call to EDITOR::FUNCALL-COMMAND-FUNCTION
....


Using :echo-area t (as in the capi:editor-pane documentation example) 
results in no error.  Are special incantations needed to get pop-up echo 
areas working in non-toplevel interfaces?

Thanks in advance,


Mike