diff --git a/hemlock/shell.lisp b/hemlock/shell.lisp
index fc3af3f0bd48a8415388967452839031bdb28791..c08cb063023000a09fb4e7880f4cf35f1ce0ea4c 100644
--- a/hemlock/shell.lisp
+++ b/hemlock/shell.lisp
@@ -353,7 +353,7 @@
   (unless (hemlock-bound-p 'process :buffer (current-buffer))
     (editor-error "Not in a process buffer."))
   (let ((stream (ext:process-pty (value process))))
-    (write-char (int-char 4) stream)
+    (write-char (code-char 4) stream)
     (force-output stream)))
 
 (defcommand "Interrupt Buffer Subprocess" (p)