diff --git a/.github/FUNDING.yml b/.github/FUNDING.yml
deleted file mode 100644
index d11d019..0000000
--- a/.github/FUNDING.yml
+++ /dev/null
@@ -1 +0,0 @@
-github: [jakubpawlowicz]
diff --git a/History.md b/History.md
index 35b484f..5cbdfa9 100644
--- a/History.md
+++ b/History.md
@@ -1,4 +1,34 @@
-[5.5.0 / 2021-xx-xx](https://github.com/clean-css/clean-css-cli/compare/5.4...HEAD)
+[5.6.3 / 2023-11-30](https://github.com/clean-css/clean-css-cli/compare/v5.6.2...v5.6.3)
+==================
+
+* Bumps clean-css dependency to 5.3.3
+
+[5.6.2 / 2023-01-19](https://github.com/clean-css/clean-css-cli/compare/v5.6.1...v5.6.2)
+==================
+
+* Bumps clean-css dependency to 5.3.2
+
+[5.6.1 / 2022-07-13](https://github.com/clean-css/clean-css-cli/compare/v5.6.0...v5.6.1)
+==================
+
+* Bumps clean-css dependency to 5.3.1.
+
+[5.6.0 / 2022-03-31](https://github.com/clean-css/clean-css-cli/compare/v5.5.2...v5.6.0)
+==================
+
+* Bumps clean-css dependency to 5.3.0.
+
+[5.5.2 / 2022-01-28](https://github.com/clean-css/clean-css-cli/compare/v5.5.1...v5.5.2)
+==================
+
+* Bumps clean-css dependency to 5.2.4.
+
+[5.5.1 / 2022-01-26](https://github.com/clean-css/clean-css-cli/compare/v5.5.0...v5.5.1)
+==================
+
+* Bumps clean-css dependency to 5.2.3.
+
+[5.5.0 / 2021-12-08](https://github.com/clean-css/clean-css-cli/compare/5.4...v5.5.0)
 ==================
 
 * Adds a new `--watch` switch, which makes CLI re-run optimizations when watched file(s) change.
diff --git a/README.md b/README.md
index fa1fe1b..49a7a9f 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,8 @@ clean-css-cli is a command-line interface to [clean-css](https://github.com/jaku
 
 Previously a part of clean-css it's a separate package since clean-css 4.0.
 
+__IMPORTANT: clean-css-cli is now in a [maintenance mode](https://github.com/clean-css/clean-css-cli/discussions/76). PRs are still welcome, and I will try do an occasional bugfix relase.__
+
 **Table of Contents**
 
 - [Node.js version support](#nodejs-version-support)
diff --git a/index.js b/index.js
index 07ef5b6..bfd06df 100644
--- a/index.js
+++ b/index.js
@@ -100,6 +100,7 @@ function cli(process, beforeMinifyCallback) {
 
   if (program.rawArgs.indexOf('-O0') > -1) {
     options.level[0] = true;
+    options.level[1] = false;
   }
 
   if (program.rawArgs.indexOf('-O1') > -1) {
diff --git a/package-lock.json b/package-lock.json
index 15deb08..f06ecb2 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "clean-css-cli",
-  "version": "5.4.2",
+  "version": "5.6.3",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -56,9 +56,9 @@
       }
     },
     "clean-css": {
-      "version": "5.2.2",
-      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-5.2.2.tgz",
-      "integrity": "sha512-/eR8ru5zyxKzpBLv9YZvMXgTSSQn7AdkMItMYynsFgGwTveCRVam9IUPFloE85B4vAIj05IuKmmEoV7/AQjT0w==",
+      "version": "5.3.3",
+      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-5.3.3.tgz",
+      "integrity": "sha512-D5J+kHaVb/wKSFcyyV75uCn8fiY4sV38XJoe4CUyGQ+mOU/fMVYUdH1hJC+CJQ5uY3EnW27SbJYS4X8BiLrAFg==",
       "requires": {
         "source-map": "~0.6.0"
       },
@@ -100,9 +100,9 @@
       }
     },
     "core-util-is": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/core-util-is/-/core-util-is-1.0.2.tgz",
-      "integrity": "sha1-tf1UIgqivFq1eqtxQMlAdUUDwac=",
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/core-util-is/-/core-util-is-1.0.3.tgz",
+      "integrity": "sha512-ZQBvi1DcpJ4GDqanjucZ2Hj3wEO5pZDS89BWbkcrvdxksJorwUDDZamX9ldFkp9aw2lmBDLgkObEA4DWNJ9FYQ==",
       "dev": true
     },
     "date-now": {
@@ -128,9 +128,9 @@
       },
       "dependencies": {
         "domelementtype": {
-          "version": "2.1.0",
-          "resolved": "https://registry.npmjs.org/domelementtype/-/domelementtype-2.1.0.tgz",
-          "integrity": "sha512-LsTgx/L5VpD+Q8lmsXSHW2WpA+eBlZ9HPf3erD1IoPF00/3JKHZ3BknUVA2QGDNu69ZNmyFmCWBSO45XjYKC5w==",
+          "version": "2.2.0",
+          "resolved": "https://registry.npmjs.org/domelementtype/-/domelementtype-2.2.0.tgz",
+          "integrity": "sha512-DtBMo82pv1dFtUmHyr48beiuq792Sxohr+8Hm9zoxklYPfa6n0Z3Byjj2IV7bmr2IyqClnqEQhfgHJJ5QF0R5A==",
           "dev": true
         },
         "entities": {
@@ -199,9 +199,9 @@
       }
     },
     "follow-redirects": {
-      "version": "1.13.0",
-      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.13.0.tgz",
-      "integrity": "sha512-aq6gF1BEKje4a9i9+5jimNFIpq4Q1WiwBToeRK5NvZBd/TRsmW8BsJfOEGkr76TbOyPVD3OVDN910EcUNtRYEA==",
+      "version": "1.14.8",
+      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.14.8.tgz",
+      "integrity": "sha512-1x0S9UVJHsQprFcEC/qnNzBLcIxsjAV905f/UkQxbclCsoTWlacCNOpQa/anodLl2uaEKFhfWOvM2Qg77+15zA==",
       "dev": true
     },
     "fs.realpath": {
@@ -307,31 +307,41 @@
       "dev": true
     },
     "jshint": {
-      "version": "2.12.0",
-      "resolved": "https://registry.npmjs.org/jshint/-/jshint-2.12.0.tgz",
-      "integrity": "sha512-TwuuaUDmra0JMkuqvqy+WGo2xGHSNjv1BA1nTIgtH2K5z1jHuAEeAgp7laaR+hLRmajRjcrM71+vByBDanCyYA==",
+      "version": "2.13.4",
+      "resolved": "https://registry.npmjs.org/jshint/-/jshint-2.13.4.tgz",
+      "integrity": "sha512-HO3bosL84b2qWqI0q+kpT/OpRJwo0R4ivgmxaO848+bo10rc50SkPnrtwSFXttW0ym4np8jbJvLwk5NziB7jIw==",
       "dev": true,
       "requires": {
         "cli": "~1.0.0",
         "console-browserify": "1.1.x",
         "exit": "0.1.x",
         "htmlparser2": "3.8.x",
-        "lodash": "~4.17.19",
+        "lodash": "~4.17.21",
         "minimatch": "~3.0.2",
-        "shelljs": "0.3.x",
         "strip-json-comments": "1.0.x"
+      },
+      "dependencies": {
+        "minimatch": {
+          "version": "3.0.8",
+          "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.0.8.tgz",
+          "integrity": "sha512-6FsRAQsxQ61mw+qP1ZzbL9Bc78x2p5OqNgNpnoAFLTrX8n5Kxph0CsnhmKKNXTWjXqU5L0pGPR7hYk+XWZr60Q==",
+          "dev": true,
+          "requires": {
+            "brace-expansion": "^1.1.7"
+          }
+        }
       }
     },
     "lodash": {
-      "version": "4.17.20",
-      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.20.tgz",
-      "integrity": "sha512-PlhdFcillOINfeV7Ni6oF1TAEayyZBoZ8bcshTHqOYJYlrqzRK5hagpagky5o4HfCzzd1TRkXPMFq6cKk9rGmA==",
+      "version": "4.17.21",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
+      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==",
       "dev": true
     },
     "minimatch": {
-      "version": "3.0.4",
-      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.0.4.tgz",
-      "integrity": "sha512-yJHVQEhyqPLUTgt9B83PXu6W3rx4MvvHvSUvToogpwoGDOUQ+yDrR0HRot+yOCdCO7u4hX3pWft6kWBBcqh0UA==",
+      "version": "3.1.2",
+      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.1.2.tgz",
+      "integrity": "sha512-J7p63hRiAjw1NDEww1W7i37+ByIrOWO5XQQAzZ3VOcL0PNybwpfmV/N05zFAzwQ9USyEcX6t3UO+K5aqBQOIHw==",
       "requires": {
         "brace-expansion": "^1.1.7"
       }
@@ -385,12 +395,6 @@
       "integrity": "sha1-kl0mAdOaxIXgkc8NpcbmlNw9yv8=",
       "dev": true
     },
-    "shelljs": {
-      "version": "0.3.0",
-      "resolved": "https://registry.npmjs.org/shelljs/-/shelljs-0.3.0.tgz",
-      "integrity": "sha1-NZbmMHp4FUT1kfN9phg2DzHbV7E=",
-      "dev": true
-    },
     "source-map": {
       "version": "0.5.7",
       "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.5.7.tgz",
diff --git a/package.json b/package.json
index 65176d4..43f5572 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "clean-css-cli",
-  "version": "5.4.2",
+  "version": "5.6.3",
   "description": "A command-line interface to clean-css CSS optimization library",
   "scripts": {
     "check": "jshint ./bin/cleancss .",
@@ -35,13 +35,13 @@
   "homepage": "https://github.com/clean-css/clean-css-cli#readme",
   "dependencies": {
     "chokidar": "^3.5.2",
-    "clean-css": "^5.2.2",
+    "clean-css": "^5.3.3",
     "commander": "7.x",
     "glob": "^7.1.6"
   },
   "devDependencies": {
     "http-proxy": "1.x",
-    "jshint": "^2.12.0",
+    "jshint": "^2.13.0",
     "source-map": "0.5.x",
     "vows": "^0.8.3"
   },
diff --git a/test/binary-test.js b/test/binary-test.js
index 65d6673..d9848e2 100644
--- a/test/binary-test.js
+++ b/test/binary-test.js
@@ -156,6 +156,13 @@ vows.describe('cleancss')
       }
     })
   })
+  .addBatch({
+    'level 0 optimizations': pipedContext('a{color:#ff0000;margin:0 0 0 0}', '-O0', {
+      'should skip all optimizations': function (error, stdout) {
+        assert.equal(stdout, 'a{color:#ff0000;margin:0 0 0 0}');
+      }
+    })
+  })
   .addBatch({
     'enable restructuring optimizations': pipedContext('div{margin-top:0}.one{margin:0}.two{display:block;margin-top:0}', '-O2 restructureRules:on', {
       'should do basic optimizations only': function (error, stdout) {
diff --git a/test/fixtures/unsupported/selectors-ie7.css b/test/fixtures/unsupported/selectors-ie7.css
index 3f2fc3e..d43708e 100644
--- a/test/fixtures/unsupported/selectors-ie7.css
+++ b/test/fixtures/unsupported/selectors-ie7.css
@@ -2,15 +2,15 @@ p:focus{top:0}
 p:before{top:0}
 p:after{top:0}
 p:root{top:0}
-p:nth-of-type(1){top:0}
-p:nth-last-of-type(1){top:0}
+p:first-of-type{top:0}
+p:last-of-type{top:0}
 p:first-of-type{top:0}
 p:last-of-type{top:0}
 p:only-of-type{top:0}
 p:only-child{top:0}
 p:last-child{top:0}
-p:nth-child(1){top:0}
-p:nth-last-child(1){top:0}
+p:first-child{top:0}
+p:last-child{top:0}
 p:empty{top:0}
 p:target{top:0}
 p:checked{top:0}
diff --git a/test/fixtures/unsupported/selectors-ie8.css b/test/fixtures/unsupported/selectors-ie8.css
index 2d01251..fb8a104 100644
--- a/test/fixtures/unsupported/selectors-ie8.css
+++ b/test/fixtures/unsupported/selectors-ie8.css
@@ -1,13 +1,13 @@
 p:root{top:0}
-p:nth-of-type(1){top:0}
-p:nth-last-of-type(1){top:0}
+p:first-of-type{top:0}
+p:last-of-type{top:0}
 p:first-of-type{top:0}
 p:last-of-type{top:0}
 p:only-of-type{top:0}
 p:only-child{top:0}
 p:last-child{top:0}
-p:nth-child(1){top:0}
-p:nth-last-child(1){top:0}
+p:first-child{top:0}
+p:last-child{top:0}
 p:empty{top:0}
 p:target{top:0}
 p:checked{top:0}