diff --git a/roles/ubuntu_base/tasks/users.yml b/roles/ubuntu_base/tasks/users.yml
index dad2a2a..010666e 100644
--- a/roles/ubuntu_base/tasks/users.yml
+++ b/roles/ubuntu_base/tasks/users.yml
@@ -18,5 +18,5 @@
 - name: "Add ssh authorized_keys to root user"
   authorized_key:
     user: "root"
-    key: "{{ users | default([]) | map(attribute='ssh_keys') | join('\n') }}"
+    key: "{{ users | default([]) | map(attribute='ssh_keys') | flatten | join('\n') }}"
     exclusive: true