diff --git a/roles/vikunja/templates/config.json.j2 b/roles/vikunja/templates/config.json.j2
index e477743..d10aba3 100644
--- a/roles/vikunja/templates/config.json.j2
+++ b/roles/vikunja/templates/config.json.j2
@@ -51,13 +51,13 @@
 {% endif %}
 	},
 	"mailer": {
-		"enabled": {{var_vikunja_mail_sending_enabled | json}},
+		"enabled": {{var_vikunja_mail_sending_enabled | to_json}},
 		"host": "{{var_vikunja_mail_sending_smtp_host}}",
 		"port": {{var_vikunja_mail_sending_smtp_port | string}},
 		"autthtype": "{{var_vikunja_mail_sending_smtp_authtype}}",
 		"username": "{{var_vikunja_mail_sending_smtp_username}}",
 		"password": "{{var_vikunja_mail_sending_smtp_password}}",
 		"fromemail": "{{var_vikunja_mail_sending_sender}}",
-		"forcessl": {{var_vikunja_mail_sending_smtp_force_tls | json}}
+		"forcessl": {{var_vikunja_mail_sending_smtp_force_tls | to_json}}
 	}
 }