reader/read-string produces malformed keywords in IE9

the following call: (reader/read-string "{:status :ok}") produces {"\uFFFD'status" "\uFFFD'ok"} which differs from expected {:status :ok}
the server inserts proper content-type (utf-8) header for all javascript files

the problem disappears if unicode special characters are manually replaced with their escaped equivalents ("\uFDD0") in cljs.core.keyword function in the compiled core.js file
it doesn't disappear when call to the str_STAR_ function is replaced to the concatenation operators, which suggest that the function works correctly and adds some mystery to the problem

currently I have no possibility to reproduce the problem on other system, so I'm not certain in all of the aspects