diff --git a/docs/configuring-playbook-client-element.md b/docs/configuring-playbook-client-element.md
index 1f90aca68..ec8556011 100644
--- a/docs/configuring-playbook-client-element.md
+++ b/docs/configuring-playbook-client-element.md
@@ -32,7 +32,7 @@ Alternatively, **if there is no pre-defined variable** for an Element setting yo
 
 ## Themes
 
-To change the look of Element, you can define your own themes manually by using the `matrix_client_element_settingDefaults_custom_themes` setting.
+To change the look of Element, you can define your own themes manually by using the `matrix_client_element_setting_defaults_custom_themes` setting.
 
 Or better yet, you can automatically pull it all themes provided by the [aaronraimist/element-themes](https://github.com/aaronraimist/element-themes) project by simply flipping a flag (`matrix_client_element_themes_enabled: true`).
 
diff --git a/roles/custom/matrix-client-element/defaults/main.yml b/roles/custom/matrix-client-element/defaults/main.yml
index f238636bf..133f9d94a 100644
--- a/roles/custom/matrix-client-element/defaults/main.yml
+++ b/roles/custom/matrix-client-element/defaults/main.yml
@@ -207,14 +207,14 @@ matrix_client_element_themes_repository_version: master
 # Controls the default theme
 matrix_client_element_default_theme: 'light'
 
-# Controls the `settingsDefault.custom_themes` setting of the Element configuration.
+# Controls the `setting_defaults.custom_themes` setting of the Element configuration.
 # You can use this setting to define custom themes.
 #
 # Also, look at `matrix_client_element_themes_enabled` for a way to pull in a bunch of custom themes automatically.
 # If you define your own themes here and set `matrix_client_element_themes_enabled: true`, your themes will be preserved as well.
 #
 # Note that for a custom theme to work well, all Element instances that you use must have the same theme installed.
-matrix_client_element_settingDefaults_custom_themes: []  # noqa var-naming
+matrix_client_element_setting_defaults_custom_themes: []  # noqa var-naming
 
 # Default Element configuration template which covers the generic use case.
 # You can customize it by controlling the various variables inside it.
diff --git a/roles/custom/matrix-client-element/tasks/prepare_themes.yml b/roles/custom/matrix-client-element/tasks/prepare_themes.yml
index 70646c94c..194335b2f 100644
--- a/roles/custom/matrix-client-element/tasks/prepare_themes.yml
+++ b/roles/custom/matrix-client-element/tasks/prepare_themes.yml
@@ -30,7 +30,7 @@
 
     - name: Load Element theme
       ansible.builtin.set_fact:
-        matrix_client_element_settingDefaults_custom_themes: "{{ matrix_client_element_settingDefaults_custom_themes + [item['content'] | b64decode | from_json] }}"  # noqa var-naming
+        matrix_client_element_setting_defaults_custom_themes: "{{ matrix_client_element_setting_defaults_custom_themes + [item['content'] | b64decode | from_json] }}"  # noqa var-naming
       with_items: "{{ matrix_client_element_theme_file_contents.results }}"
 
 #
diff --git a/roles/custom/matrix-client-element/tasks/validate_config.yml b/roles/custom/matrix-client-element/tasks/validate_config.yml
index 4f5fd0ee7..e78bd4a71 100644
--- a/roles/custom/matrix-client-element/tasks/validate_config.yml
+++ b/roles/custom/matrix-client-element/tasks/validate_config.yml
@@ -37,6 +37,7 @@
     - {'old': 'matrix_client_element_showLabsSettings', 'new': 'matrix_client_element_show_lab_settings'}
     - {'old': 'matrix_client_element_permalinkPrefix', 'new': 'matrix_client_element_permalink_prefix'}
     - {'old': 'matrix_client_element_roomdir_servers', 'new': 'matrix_client_element_room_directory_servers'}
+    - {'old': 'matrix_client_element_settingDefaults_custom_themes', 'new': 'matrix_client_element_setting_defaults_custom_themes'}
 
 - when: matrix_client_element_container_labels_traefik_enabled | bool
   block:
diff --git a/roles/custom/matrix-client-element/templates/config.json.j2 b/roles/custom/matrix-client-element/templates/config.json.j2
index 5465395df..9b5ff153b 100644
--- a/roles/custom/matrix-client-element/templates/config.json.j2
+++ b/roles/custom/matrix-client-element/templates/config.json.j2
@@ -8,8 +8,8 @@
 			"base_url": {{ matrix_client_element_default_is_url | string | to_json }}
 		}
 	},
-	"settingDefaults": {
-		"custom_themes": {{ matrix_client_element_settingDefaults_custom_themes | to_json }}
+	"setting_defaults": {
+		"custom_themes": {{ matrix_client_element_setting_defaults_custom_themes | to_json }}
 	},
 	"default_theme": {{ matrix_client_element_default_theme | string | to_json }},
 	"default_country_code": {{ matrix_client_element_default_country_code | string | to_json }},