diff --git a/Makefile b/Makefile
index b7895f0..3cfb9e5 100644
--- a/Makefile
+++ b/Makefile
@@ -109,12 +109,12 @@ brainux:
 		echo "Debootstrap is only available in Linux!"; \
 		exit 1; \
 	fi
-	mkdir -p brainux
+	sudo mkdir -p brainux
 	@if [ "$(CI)" = "true" ]; then \
 		echo "I'm in CI and debootstrap without cache."; \
-		sudo debootstrap --arch=armel --foreign buster brainux/; \
+		sudo debootstrap --arch=armel --foreign bullseye brainux/; \
 	else \
-		sudo debootstrap --arch=armel --foreign buster brainux/ http://localhost:65432/debian/; \
+		sudo debootstrap --arch=armel --foreign bullseye brainux/ http://localhost:65432/debian/; \
 	fi
 	sudo cp /usr/bin/qemu-arm-static brainux/usr/bin/
 	sudo cp ./os-brainux/setup_brainux.sh brainux/
diff --git a/README.md b/README.md
index 2b33160..52375c5 100644
--- a/README.md
+++ b/README.md
@@ -81,8 +81,8 @@ Build Linux
 1. Confirm that `linux-brain/arch/arm/boot/zImage` exists.
 
 
-Bootstrap Debian 10 (buster)
-----------------------------
+Bootstrap Debian 11 (bullseye)
+------------------------------
 
 1. Run `make ldefconfig lbuild`.
 
diff --git a/os-brainux/override/usr/lib/os-release b/os-brainux/override/usr/lib/os-release
index e60947d..ec1f499 100644
--- a/os-brainux/override/usr/lib/os-release
+++ b/os-brainux/override/usr/lib/os-release
@@ -1,8 +1,8 @@
-PRETTY_NAME="Brainux GNU/Linux 10 (buster)"
+PRETTY_NAME="Brainux GNU/Linux 11 (bullseye)"
 NAME="Brainux GNU/Linux"
-VERSION_ID="10"
-VERSION="10 (buster)"
-VERSION_CODENAME=buster
+VERSION_ID="11"
+VERSION="11 (bullseye)"
+VERSION_CODENAME=bullseye
 ID=debian
 HOME_URL="https://github.com/brain-hackers/README"
 SUPPORT_URL="https://github.com/brain-hackers/buildbrain"
diff --git a/os-brainux/setup_brainux.sh b/os-brainux/setup_brainux.sh
index bdbaa10..3f919e4 100755
--- a/os-brainux/setup_brainux.sh
+++ b/os-brainux/setup_brainux.sh
@@ -20,12 +20,12 @@ else
 fi
 
 cat <<EOF > /etc/apt/sources.list
-deb http://${REPO}/debian buster main contrib non-free
-deb-src http://${REPO}/debian buster main contrib non-free
-deb http://${REPO}/debian buster-updates main contrib non-free
-deb-src http://${REPO}/debian buster-updates main contrib non-free
-deb http://${REPO_SECURITY}/debian-security buster/updates main contrib non-free
-deb-src http://${REPO_SECURITY}/debian-security buster/updates main contrib non-free
+deb http://${REPO}/debian bullseye main contrib non-free
+deb-src http://${REPO}/debian bullseye main contrib non-free
+deb http://${REPO}/debian bullseye-updates main contrib non-free
+deb-src http://${REPO}/debian bullseye-updates main contrib non-free
+deb http://${REPO_SECURITY}/debian-security bullseye-security/updates main contrib non-free
+deb-src http://${REPO_SECURITY}/debian-security bullseye-security/updates main contrib non-free
 EOF
 
 cat <<EOF > /etc/apt/apt.conf.d/90-norecommend
@@ -43,6 +43,8 @@ echo "$TIMEZONE" > /etc/timezone && \
     dpkg-reconfigure -f noninteractive locales && \
     update-locale LANG=en_US.UTF-8
 
+LANG=en_US.UTF-8
+
 rm /etc/localtime
 ln -s /usr/share/zoneinfo/Asia/Tokyo /etc/localtime
 
@@ -51,7 +53,7 @@ DEBIAN_FRONTEND=noninteractive \
     apt install -y dialog sudo \
                    libjpeg-dev libfreetype6 libfreetype6-dev zlib1g-dev \
                    xserver-xorg xserver-xorg-video-fbdev xserver-xorg-dev xserver-xorg-input-evdev xinput-calibrator xorg-dev x11-apps xinit \
-                   openbox obconf obmenu jwm \
+                   jwm \
                    weston xwayland \
                    bash tmux vim htop \
                    midori pcmanfm lxterminal xterm gnome-terminal fbterm uim-fep uim-anthy fonts-noto-cjk \
@@ -104,11 +106,11 @@ EOF
 
 # Get wild
 cat <<EOF > /etc/apt/sources.list
-deb http://deb.debian.org/debian buster main contrib non-free
-deb-src http://deb.debian.org/debian buster main contrib non-free
-deb http://deb.debian.org/debian buster-updates main contrib non-free
-deb-src http://deb.debian.org/debian buster-updates main contrib non-free
-deb http://deb.debian.org/debian-security buster/updates main contrib non-free
-deb-src http://deb.debian.org/debian-security buster/updates main contrib non-free
+deb http://deb.debian.org/debian bullseye main contrib non-free
+deb-src http://deb.debian.org/debian bullseye main contrib non-free
+deb http://deb.debian.org/debian bullseye-updates main contrib non-free
+deb-src http://deb.debian.org/debian bullseye-updates main contrib non-free
+deb http://deb.debian.org/debian-security bullseye-security/updates main contrib non-free
+deb-src http://deb.debian.org/debian-security bullseye-security/updates main contrib non-free
 EOF