diff --git a/editor/editor.asd b/editor/editor.asd
index c994b0a..65e069f 100644
--- a/editor/editor.asd
+++ b/editor/editor.asd
@@ -3,7 +3,7 @@
 (asdf:defsystem #:editor
   :version "0.1.0"
   :serial t
-  :depends-on (#:user-side-compiler #:trivial-gray-streams)
+  :depends-on (#:user-side-compiler #:trivial-gray-streams #:split-sequence)
   :components ((:file "package")
                (:file "editor")
                (:file "binary-build")))
diff --git a/editor/editor.lisp b/editor/editor.lisp
index 4e2a203..be805ff 100644
--- a/editor/editor.lisp
+++ b/editor/editor.lisp
@@ -414,6 +414,23 @@ serial connection the editor normally runs under.")
           :do (write-string (line-content line) output)
               (terpri output))))
 
+(defmethod (setf buffer-string) (new-value (buffer buffer))
+  (declare (optimize (debug 3)))
+  (let ((lines (split-sequence #\Newline new-value)))
+    (setf (first-line buffer) (make-instance 'line))
+    (set-line-text (first-line buffer) (first lines))
+    (loop :for lines-left := (rest lines) :then (rest lines-left)
+          :until (null lines-left)
+          :for line := (first lines-left)
+          :for prev-line := (first-line buffer) :then line-obj
+          :for line-obj := (make-instance 'line :prev-line prev-line)
+          :do (setf (next-line prev-line) line-obj)
+              (set-line-text line-obj line))
+    (setf (top-line (buffer-view buffer)) (first-line buffer)
+          (bottom-line (buffer-view buffer)) nil
+          (cursor-line (cursor buffer)) (first-line buffer)
+          (cursor-column (cursor buffer)) 0)))
+
 (defmethod update-buffer-cursor ((buffer buffer))
   "Makes sure the screen cursor is the same as BUFFER's logical cursor.
 Additionally ensures correct line numbers on the way, as a bonus."
diff --git a/editor/package.lisp b/editor/package.lisp
index 8a22b55..59d979a 100644
--- a/editor/package.lisp
+++ b/editor/package.lisp
@@ -1,5 +1,5 @@
 ;;;; package.lisp
 
 (defpackage #:editor
-  (:use #:cl #:trivial-gray-streams)
+  (:use #:cl #:trivial-gray-streams #:split-sequence)
   (:export #:main))