diff --git a/classes/Cache_Local.php b/classes/Cache_Local.php
index 8ac634a3e..dd3548111 100644
--- a/classes/Cache_Local.php
+++ b/classes/Cache_Local.php
@@ -11,7 +11,14 @@ class Cache_Local implements Cache_Adapter {
 	}
 
 	public function set_dir(string $dir) : void {
-		$this->dir = Config::get(Config::CACHE_DIR) . "/" . basename(clean($dir));
+		$cache_dir = Config::get(Config::CACHE_DIR);
+
+		// use absolute path local to current dir if CACHE_DIR is relative
+		// TODO: maybe add a special method to Config() for this?
+		if ($cache_dir[0] != '/')
+			$cache_dir = dirname(__DIR__) . "/$cache_dir";
+
+		$this->dir = $cache_dir . "/" . basename(clean($dir));
 
 		$this->make_dir();
 	}