Index: src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php
===================================================================
--- src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php	(revision 48524)
+++ src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php	(working copy)
@@ -581,6 +581,12 @@
 			update_post_meta( $new_attachment_id, '_wp_attachment_image_alt', wp_slash( $image_alt ) );
 		}
 
+		if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
+			// Set a custom header with the attachment_id.
+			// Used by the browser/client to resume creating image sub-sizes after a PHP fatal error.
+			header( 'X-WP-Upload-Attachment-ID: ' . $new_attachment_id );
+		}
+
 		// Generate image sub-sizes and meta.
 		$new_image_meta = wp_generate_attachment_metadata( $new_attachment_id, $saved['path'] );