Cannot jzon:parse from pathname on LispWorks

[Zulu-Inuoe]

Error: External format (:UTF-8 :EOL-STYLE :LF) produces characters of type CHARACTER, which is not a subtype of the specified element-type BASE-CHAR.
  1 (abort) Return to top loop level 0.

LispWorks' cl:open defaults :element-type to lispworks:*default-character-element-type* per http://www.lispworks.com/documentation/lw70/LW/html/lw-387.htm

When this is base-char and providing :external-format :utf-8, it complains that it may not be able to decode everything into a base-char