diff --git a/gmi.rkt b/gmi.rkt
index c9d9b0e..30751ed 100644
--- a/gmi.rkt
+++ b/gmi.rkt
@@ -2,7 +2,7 @@
 
 (provide (contract-out
           [render (-> document? void?)]
-          [parse (-> (listof string?) document?)]
+          [parse (-> input-port? document?)]
           [match-link (-> document? integer? (or/c url? #f))]
           [struct document ((items (listof (or/c text? link? pre?))))]))
 
@@ -30,7 +30,7 @@
                   (car split))
               link-#))))
 
-(define (parse lines)
+(define (parse body-port)
   (define (iter document lines state link-id)
     ;; when there are no more lines, we have finished parsing.
     (if (empty? lines)
@@ -95,7 +95,7 @@
                  'normal
                  link-id)])))
 
-  (document (iter (list) lines 'normal 1)))
+  (document (iter (list) (port->lines body-port) 'normal 1)))
 
 ;;;
 ;;; RENDERING