diff --git a/roles/custom/matrix-synapse-admin/defaults/main.yml b/roles/custom/matrix-synapse-admin/defaults/main.yml
index b42675d95..013a97d6b 100644
--- a/roles/custom/matrix-synapse-admin/defaults/main.yml
+++ b/roles/custom/matrix-synapse-admin/defaults/main.yml
@@ -187,7 +187,7 @@ matrix_synapse_admin_configuration_default:
 matrix_synapse_admin_configuration_extension_json: '{}'
 
 # This is similar to `matrix_synapse_admin_configuration_extension_json`, but intended for use by playbook or group vars
-matrix_synapse_admin_configuration_extension_json_auto: {}
+matrix_synapse_admin_configuration_extension_json_auto: '{}'
 
 matrix_synapse_admin_configuration_extension: "{{ matrix_synapse_admin_configuration_extension_json_auto | from_json | combine(matrix_synapse_admin_configuration_extension_json | from_json if matrix_synapse_admin_configuration_extension_json | from_json is mapping else {}, recursive=True) }}"