diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index b00767dbf9abdb..3008f9a82a25a7 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -357,6 +357,7 @@ class WP_Theme_JSON_Gutenberg {
 		'styles',
 		'templateParts',
 		'title',
+		'slug',
 		'version',
 	);
 
diff --git a/schemas/json/theme.json b/schemas/json/theme.json
index bdfea7279f67ac..77808d8783ea40 100644
--- a/schemas/json/theme.json
+++ b/schemas/json/theme.json
@@ -2696,6 +2696,10 @@
 			"type": "string",
 			"description": "Title of the global styles variation. If not defined, the file name will be used."
 		},
+		"slug": {
+			"type": "string",
+			"description": "Slug of the global styles variation. If not defined, the kebab-case title will be used."
+		},
 		"description": {
 			"type": "string",
 			"description": "Description of the global styles variation."