diff --git a/tests/dev-ptmx b/tests/dev-ptmx
index 760c244..72bb974 100644
--- a/tests/dev-ptmx
+++ b/tests/dev-ptmx
@@ -117,7 +117,7 @@ END
 # use script to create a fake tty
 # run all tests as root and as a normal user (the latter requires ptmxmode=666)
 script -qfc "$prefix {{ CMD }} --mode={{ MODE }} --variant=apt \
-	--include=gcc,libc6-dev,python3 \
+	--include=gcc,libc6-dev,python3,adduser \
 	--customize-hook='chroot \"\$1\" adduser --gecos user --disabled-password user' \
 	--customize-hook='chroot \"\$1\" python3 -c \"import pty; print(pty.openpty())\"' \
 	--customize-hook='chroot \"\$1\" runuser -u user -- python3 -c \"import pty; print(pty.openpty())\"' \