diff --git a/composer.json b/composer.json
index a45dcb938..283a31a81 100644
--- a/composer.json
+++ b/composer.json
@@ -54,7 +54,7 @@
         "shardj/zf1-future": "^1.23.5",
         "simshaun/recurr": "^5",
         "tedivm/jshrink": "^1.6.8",
-        "wikimedia/less.php": "^3.2.1",
+        "wikimedia/less.php": "^5.5.0",
         "zircote/swagger-php": "^6.0"
     },
     "autoload": {
diff --git a/composer.lock b/composer.lock
index 1ed0a1bfb..ac04f0f9d 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "c6738a7a85d9ba24924250d8319489cd",
+    "content-hash": "4c0655bff537335cf97f58b1b28466bf",
     "packages": [
         {
             "name": "brick/math",
@@ -4912,28 +4912,28 @@
         },
         {
             "name": "wikimedia/less.php",
-            "version": "v3.2.1",
+            "version": "v5.5.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/wikimedia/less.php.git",
-                "reference": "0d5b30ba792bdbf8991a646fc9c30561b38a5559"
+                "reference": "f12e470d4fb4478b8af759d4c5da99707af3db10"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/wikimedia/less.php/zipball/0d5b30ba792bdbf8991a646fc9c30561b38a5559",
-                "reference": "0d5b30ba792bdbf8991a646fc9c30561b38a5559",
+                "url": "https://api.github.com/repos/wikimedia/less.php/zipball/f12e470d4fb4478b8af759d4c5da99707af3db10",
+                "reference": "f12e470d4fb4478b8af759d4c5da99707af3db10",
                 "shasum": ""
             },
             "require": {
-                "php": ">=7.2.9"
+                "php": ">=8.1"
             },
             "require-dev": {
-                "mediawiki/mediawiki-codesniffer": "40.0.1",
-                "mediawiki/mediawiki-phan-config": "0.12.0",
-                "mediawiki/minus-x": "1.1.1",
+                "mediawiki/mediawiki-codesniffer": "48.0.0",
+                "mediawiki/mediawiki-phan-config": "0.17.0",
+                "mediawiki/minus-x": "1.1.3",
                 "php-parallel-lint/php-console-highlighter": "1.0.0",
-                "php-parallel-lint/php-parallel-lint": "1.3.2",
-                "phpunit/phpunit": "^8.5"
+                "php-parallel-lint/php-parallel-lint": "1.4.0",
+                "phpunit/phpunit": "10.5.58"
             },
             "bin": [
                 "bin/lessc"
@@ -4981,9 +4981,9 @@
             ],
             "support": {
                 "issues": "https://github.com/wikimedia/less.php/issues",
-                "source": "https://github.com/wikimedia/less.php/tree/v3.2.1"
+                "source": "https://github.com/wikimedia/less.php/tree/v5.5.0"
             },
-            "time": "2023-02-03T06:43:41+00:00"
+            "time": "2025-12-18T22:27:01+00:00"
         },
         {
             "name": "zircote/swagger-php",