diff --git a/src/wp-includes/canonical.php b/src/wp-includes/canonical.php
index 4c981f9a38..0818124973 100644
--- a/src/wp-includes/canonical.php
+++ b/src/wp-includes/canonical.php
@@ -150,9 +150,15 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 
 	} elseif ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() ) {
 		// rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101
-		if ( is_attachment() && !empty($_GET['attachment_id']) && ! $redirect_url ) {
-			if ( $redirect_url = get_attachment_link(get_query_var('attachment_id')) )
-				$redirect['query'] = remove_query_arg('attachment_id', $redirect['query']);
+		if ( is_attachment() && ! $redirect_url ) {
+			if ( ! empty( $_GET['attachment_id'] ) ) {
+				$redirect_url = get_attachment_link( get_query_var( 'attachment_id' ) );
+				if ( $redirect_url ) {
+					$redirect['query'] = remove_query_arg( 'attachment_id', $redirect['query'] );
+				}
+			} else {
+				$redirect_url = get_attachment_link();
+			}
 		} elseif ( is_single() && !empty($_GET['p']) && ! $redirect_url ) {
 			if ( $redirect_url = get_permalink(get_query_var('p')) )
 				$redirect['query'] = remove_query_arg(array('p', 'post_type'), $redirect['query']);