diff --git a/racket/collects/file/unzip.rkt b/racket/collects/file/unzip.rkt
index 7bca18338e..fa962f3f06 100644
--- a/racket/collects/file/unzip.rkt
+++ b/racket/collects/file/unzip.rkt
@@ -211,12 +211,23 @@
                                                     (msdos-date+time->seconds date time utc?)))
                   (read-entry filename dir? in))
 
+              ;; Read until the end of the deflated stream when compressed size unknown
+              (when (bitwise-bit-set? bits 3)
+                (let loop () (unless (eof-object? (read-bytes 1024 in)) (loop))))
+
               (when t (kill-thread t)))
+
             (lambda ()
               ;; appnote VI-C : if bit 3 is set, then the file data
               ;; is immediately followed by a data descriptor
+              ;; appnote 4.3.9.3 : the value 0x08074b50 may appear
+              ;; as a data descriptor signature immediately
+              ;; following the file data
               (if (bitwise-bit-set? bits 3)
-                  (skip-bytes 12 in)
+                  ;; Read possibly signed data descriptor
+                  (let ([maybe-signature (read-int 4)])
+                    (skip-bytes (if (= maybe-signature #x08074b50) 12 8)
+                                in))
                   (skip-bytes (- (+ mark compressed) (file-position in)) in)))))
       (void))))