This page is part of the web mail archives of SRFI 6 from before July 7th, 2015. The new archives for SRFI 6 contain all messages, not just those from before July 7th, 2015.
From the SRFI:
(OPEN-OUTPUT-STRING) ;procedure
Returns an output port that will accumulate characters for retrieval
by GET-OUTPUT-STRING. The port can be closed by the procedure
CLOSE-INPUT-PORT, though its storage will be reclaimed by the ...
^^^^^
Did you mean CLOSE-OUTPUT-PORT?
-Richard