diff --git a/tests/php/validation/test-class-amp-validation-manager.php b/tests/php/validation/test-class-amp-validation-manager.php
index 6178dc22e24..6b34000c130 100644
--- a/tests/php/validation/test-class-amp-validation-manager.php
+++ b/tests/php/validation/test-class-amp-validation-manager.php
@@ -1382,6 +1382,9 @@ public function test_add_block_source_comments( $content, $expected, $query ) {
 
 		$rendered_block = do_blocks( AMP_Validation_Manager::add_block_source_comments( $content ) );
 
+		// Remove class name injected by gutenberg_render_layout_support_flag().
+		$rendered_block = preg_replace( '/(?<= class=")wp-container-\w+ /', '', $rendered_block );
+
 		$expected = str_replace(
 			[
 				'{{post_id}}',