diff --git a/tmux.conf b/tmux.conf
index a4f3a2e..5f5b3f6 100644
--- a/tmux.conf
+++ b/tmux.conf
@@ -30,4 +30,4 @@ source-file ~/.dotfiles/tmux.d/status-line
 bind-key C-c new-window
 
 # pbcopy できるようにする
-set -g default-command "reattach-to-user-namespace -l ${SHELL}"
+set-option -g default-command "reattach-to-user-namespace -l ${SHELL}"