diff --git a/roles/hackmd/tasks/main.yml b/roles/hackmd/tasks/main.yml
index f97c914..7432141 100644
--- a/roles/hackmd/tasks/main.yml
+++ b/roles/hackmd/tasks/main.yml
@@ -32,14 +32,14 @@
 
 - name: Configure hackmd
   template: src=config.json.j2 dest=/opt/hackmd-{{hackmd_version}}/config.json owner=hackmd
-  notify: Restart hackmd
   register: hackmd_config
+  notify: Restart hackmd
 
 - name: Build hackmd frontend
   command: /usr/bin/npm run build chdir=/opt/hackmd-{{hackmd_version}}
   become: true
   become_user: hackmd
-  when: hackmd_unarchive.changed or hackmd_config.changed
+  when: (hackmd_unarchive is defined and hackmd_unarchive.changed) or (hackmd_config is defined and hackmd_config.changed)
 
 - name: Configure PostgreSQL database
   postgresql_db: name={{ hackmd_dbname }}