diff --git a/TODO.md b/TODO.md
index 8baa05a3..51a55648 100644
--- a/TODO.md
+++ b/TODO.md
@@ -2,7 +2,7 @@
 
 ## Before release
 
-- readline
+- Debug mode always on, but prevent pdb if no terminal
 - Add Gentoo instructions
 - Finish the README.md
 - Build final AppImage and test media opening
diff --git a/build-appimage.sh b/build-appimage.sh
index 5fb08bce..2590efcd 100755
--- a/build-appimage.sh
+++ b/build-appimage.sh
@@ -75,7 +75,7 @@ install_apt_packages() {
         libglfw3-dev libgles2-mesa-dev libjpeg-turbo8-dev zlib1g-dev \
         libtiff5-dev liblcms2-dev libwebp-dev  libopenjp2-7-dev libssl-dev \
         python3-dev python3-setuptools python3-pip libgdbm-dev libc6-dev \
-        zlib1g-dev libsqlite3-dev libffi-dev openssl \
+        zlib1g-dev libsqlite3-dev libffi-dev openssl libreadline-dev \
         desktop-file-utils  # for appimage-lint.sh
 
     /usr/sbin/update-ccache-symlinks