diff --git a/README.md b/README.md
index b5dff03..6b504a3 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # Dependencies
 
 - [CHICKEN Scheme](https://call-cc.org) 5 or 6;
-- A few CHICKEN extensions, installable using `chicken-install -s format html-parser openssl http-client matchable srfi-18`.
+- A few CHICKEN extensions, installable using `chicken-install -s format html-parser openssl http-client matchable`.
 
 # Building
 
diff --git a/rain.scm b/rain.scm
index c55dd5c..7440640 100644
--- a/rain.scm
+++ b/rain.scm
@@ -1,5 +1,3 @@
-(define parallel 1)
-
 (define (find-comic-image index)
   (call-with-current-continuation
    (lambda (k)
@@ -20,24 +18,13 @@
   (format (current-error-port) "* downloaded comic image ~a~%" index))
 
 (define (download-all indices)
-  (format (current-error-port) "* using ~a threads~%" parallel)
-  (for-each download-batch (chop indices parallel)))
-
-(define (download-batch batch)
-  (let ((threads (map (lambda (index)
-                        (make-thread
-                         (lambda ()
-                           (download-comic-image index))))
-                      batch)))
-    (for-each thread-start! threads)
-    (for-each thread-join! threads)))
+  (for-each download-comic-image indices))
 
 (define (usage)
   (format (current-error-port) "usage: ~a [OPTION ...] INDEX ...~%" (program-name))
   (format (current-error-port) "options:~%")
   (format (current-error-port) "  -h|-help        display this help message~%")
-  (format (current-error-port) "  -v|-version     display version information~%")
-  (format (current-error-port) "  -j|-parallel N  download N images in parallel~%"))
+  (format (current-error-port) "  -v|-version     display version information~%"))
 
 (define parse-command-line
   (match-lambda
@@ -45,13 +32,6 @@
      (usage))
     (((or "-v" "-version") . _)
      (format (current-error-port) "rain.scm 1.0.1~%" (program-name)))
-    (((or "-j" "-parallel") n . rest)
-     (let ((nn (string->number n)))
-       (unless nn
-         (usage)
-         (exit 1))
-       (set! parallel nn)
-       (parse-command-line rest)))
     (()
      (usage))
     (indices
diff --git a/rain.sld b/rain.sld
index ee0c24e..12d74bb 100755
--- a/rain.sld
+++ b/rain.sld
@@ -14,7 +14,6 @@ exec csi -s "$0" "$@"
    (html-parser)
    (openssl)                            ; has to be before http-client
    (http-client)
-   (matchable)
-   (srfi-18))
+   (matchable))
   (include "rain.scm")
   (begin (main (command-line-arguments))))