Hello. When running asdf:test-op on the flexi-streams 1.0.7 with SBCL some failures occur. The error message is Test (STRING= (FLEXI-STREAMS-TEST::OLD-OCTETS-TO-STRING FLEXI-STREAMS-TEST::OCTETS-VECTOR :EXTERNAL-FORMAT FLEXI-STREAMS-TEST::EXTERNAL-FORMAT) STRING) failed signalling error of type TYPE-ERROR: The value 0 is not of type (MEMBER NIL T). If I comment lines 341, 342 in test.lisp, the error does not occur. I googled for that error and found a code snippet (http://paste.lisp.org/display/73334) which reproduces the error: (with-input-from-string (in "123456") (let ((stream (flex:make-flexi-stream in)) (buffer (make-sequence 'string 3))) (read-sequence buffer stream))) The code is not correct because it creates flexi-stream on top of character but not binary stream. But the error message is the same, probably it might help you identify the reason why the tests fail. Best regards, - Anton