diff --git a/README.md b/README.md
index 9ec38ec2..0f351466 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ This is a PHP port of the [official LESS processor](https://lesscss.org).
 
 ## About
 
-The code structure of Less.php mirrors that of upstream Less.js to ensure compatibility and help reduce maintenance. The port is currently compatible with Less.js 2.5.3. Please note that "inline JavaScript expressions" (via eval or backticks) are not supported.
+The code structure of Less.php mirrors that of upstream Less.js to ensure compatibility and help reduce maintenance. The port aims to be compatible with Less.js 3.13.1. Please note that "inline JavaScript expressions" (via eval or backticks) are not supported.
 
 * [API § Caching](./API.md#caching), Less.php includes a file-based cache.
 * [API § Source maps](./API.md#source-maps), Less.php supports v3 sourcemaps.
diff --git a/test/compare.php b/test/compare.php
index 20ac6d13..1a54e321 100644
--- a/test/compare.php
+++ b/test/compare.php
@@ -7,14 +7,17 @@
 
 Options:
 
-    fixtureDir  Pass one of the /test/Fixtures/ directories.
+    fixtureDir  Pass one of the test/Fixtures/ directories.
                 The compare tool will compile each file in the "less/"
                 subdirectory, and compare it to an eponymous file in the
                 "css/" subdirectory.
+                Alternatively, pass one of the "less/" sub-sub directories
+                directly and the corresponding "css/" directory will be found
+                automatically.
 
                 - {{FIXTURE_DIR}}
 
-                Default: test/Fixtures/lessjs-2.5.3/
+                Default: test/Fixtures/lessjs-3.13.1/less/_main/
 
     --override  By default, the compare tool validates the full upstream
                 Less.js specification, as stored in the fixture's "css/"
@@ -59,7 +62,7 @@ public function cli( $args ) {
 		}
 
 		$this->compare(
-			$fixtureDir ?? __DIR__ . '/Fixtures/lessjs-2.5.3/',
+			$fixtureDir ?? 'lessjs-3.13.1',
 			$useOverride
 		);
 	}