diff --git a/wp-cache-phase2.php b/wp-cache-phase2.php
index 0cb613de..a968fb8b 100644
--- a/wp-cache-phase2.php
+++ b/wp-cache-phase2.php
@@ -854,8 +854,9 @@ function get_current_url_supercache_dir( $post_id = 0 ) {
 			}
 		} else {
 			$uri = str_replace( $site_url, '', $permalink );
-			if ( ! str_starts_with( $uri, $wp_cache_home_path ) ) {
-				$uri = rtrim( $wp_cache_home_path, '/' ) . $uri;
+			$home_path = $wp_cache_home_path ?? '';
+			if ( $home_path !== '' && ! str_starts_with( $uri, $home_path ) ) {
+				$uri = rtrim( $home_path, '/' ) . $uri;
 			}
 		}
 	} else {