diff --git a/eval-server.sld b/eval-server.sld
index 366797e..690b85d 100644
--- a/eval-server.sld
+++ b/eval-server.sld
@@ -7,6 +7,7 @@
           (scheme write)
           (only (chicken blob) blob->string)
           (only (chicken file) create-temporary-directory)
+          (chicken process-context)
           (chicken process)
           (only (srfi 4) u8vector->blob)
           (spiffy)
@@ -68,6 +69,12 @@
        (make-tar-header-for-regular-file filename bytes)
        bytes (make-tar-padding bytes)))
 
+    (define (with-current-directory dir proc)
+      (let ((old-dir (current-directory)))
+        (dynamic-wind (lambda () (change-directory dir))
+                      proc
+                      (lambda () (change-directory old-dir)))))
+
     (define (handle-the-scheme-implementation impl)
       (let ((cmdline #f)
             (environ #f)
@@ -115,23 +122,26 @@
           (error "No main.scm file in archive"))
         (let ((tempdir (create-temporary-directory)))
           (write tempdir)(newline)
-          (for-each (lambda (entry)
-                      (let ((name (car entry))
-                            (bytes (cdr entry)))
-                        (call-with-port
-                         (open-binary-output-file name)
-                         (lambda (out) (write-bytevector bytes out)))))
-                    files))
-        (let ((command (append (implementation-command-line impl)
-                               (list "main.scm")
-                               cmdline)))
-          (write command)(newline)
-          (let-values (((from-sub to-sub sub-pid from-sub-err)
-                        (process* (car command) (cdr command) environ)))
-            (write-bytevector stdin to-sub)
-            (close-output-port to-sub)
-            (set! stdout (read-all-bytes from-sub))
-            (set! stderr (read-all-bytes from-sub-err))))
+          (with-current-directory
+           tempdir
+           (lambda ()
+             (for-each (lambda (entry)
+                         (let ((name (car entry))
+                               (bytes (cdr entry)))
+                           (call-with-port
+                            (open-binary-output-file name)
+                            (lambda (out) (write-bytevector bytes out)))))
+                       files)
+             (let ((command (append (implementation-command-line impl)
+                                    (list "main.scm")
+                                    cmdline)))
+               (write command)(newline)
+               (let-values (((from-sub to-sub sub-pid from-sub-err)
+                             (process* (car command) (cdr command) environ)))
+                 (write-bytevector stdin to-sub)
+                 (close-output-port to-sub)
+                 (set! stdout (read-all-bytes from-sub))
+                 (set! stderr (read-all-bytes from-sub-err)))))))
         (send-response
          status: 'ok
          headers: `((content-type ,tar-content-type))