diff --git a/src/BlockTypesController.php b/src/BlockTypesController.php
index b742aa2d94e..dbc38806438 100644
--- a/src/BlockTypesController.php
+++ b/src/BlockTypesController.php
@@ -76,7 +76,7 @@ public function register_blocks() {
 	 */
 	public function add_data_attributes( $content, $block ) {
 		$block_name      = $block['blockName'];
-		$block_namespace = strtok( $block_name, '/' );
+		$block_namespace = strtok( $block_name ?? '', '/' );
 
 		/**
 		 * Filters the list of allowed block namespaces.