diff --git a/racket/src/cs/c/adjust-compress.rkt b/racket/src/cs/c/adjust-compress.rkt
index 0a638daa13..12281c8e3d 100644
--- a/racket/src/cs/c/adjust-compress.rkt
+++ b/racket/src/cs/c/adjust-compress.rkt
@@ -1,13 +1,17 @@
 #lang racket/base
 (require racket/file
+         racket/system
          file/gzip
          file/gunzip)
 
 (provide enable-compress!
          compress-enabled?
+         set-compress-format!
+         get-compress-format
          adjust-compress)
 
 (define compress? #f)
+(define compress-format 'lz4)
 
 (define (enable-compress!)
   (set! compress? #t))
@@ -15,6 +19,14 @@
 (define (compress-enabled?)
   compress?)
 
+(define (set-compress-format! fmt)
+  (unless (memq fmt '(lz4 gzip))
+    (error 'set-compress-format! "bad format: ~v" fmt))
+  (set! compress-format fmt))
+
+(define (get-compress-format)
+  compress-format)
+
 (define (reencode bstr encode)
   (let ([o (open-output-bytes)]
         [i (open-input-bytes bstr)])
@@ -24,15 +36,43 @@
         (loop)))
     (get-output-bytes o)))
 
-(define (adjust-compress bstr)
-  (if (bytes=? #"\0\0\0\0chez" (subbytes bstr 0 8))
-      (if compress?
-          (reencode bstr (lambda (i o) (gzip-through-ports i o #f 0)))
-          bstr)
-      (if compress?
-          bstr
-          (reencode bstr gunzip-through-ports))))
+(define (lz4 flag bstr)
+  (define o (open-output-bytes))
+  (unless (parameterize ([current-input-port (open-input-bytes bstr)]
+                         [current-output-port o])
+            (system* (find-executable-path "lz4") flag))
+    (error "lz4 failed"))
+  (get-output-bytes o))
 
+(define (adjust-compress bstr)
+  (cond
+    [(bytes=? #"\0\0\0\0chez" (subbytes bstr 0 8))
+     ;; source is not compressed
+     (cond
+       [(and compress? (eq? compress-format 'gzip))
+        (reencode bstr (lambda (i o) (gzip-through-ports i o #f 0)))]
+       [(and compress? (eq? compress-format 'lz4))
+        (lz4 "-z" bstr)]
+       [else bstr])]
+    [(bytes=? #"\4\"M\30" (subbytes bstr 0 4))
+     ;; source is LZ4
+     (cond
+       [(and compress? (eq? compress-format 'gzip))
+        (reencode (lz4 "-d" bstr) (lambda (i o) (gzip-through-ports i o #f 0)))]
+       [(and compress? (eq? compress-format 'lz4))
+        bstr]
+       [else (lz4 "-d" bstr)])]
+    [(bytes=? #"\37\213\b" (subbytes bstr 0 3))
+     ;; source is gzip
+     (cond
+       [(and compress? (eq? compress-format 'gzip))
+        bstr]
+       [(and compress? (eq? compress-format 'lz4))
+        (lz4 "-z" (reencode bstr gunzip-through-ports))]
+       [else
+        (reencode bstr gunzip-through-ports)])]
+    [else (error 'adjust-compress "unrecognized format ~s" (subbytes bstr 0 3))]))
+       
 (module+ main
   (require racket/cmdline)