diff --git a/.stylelintrc b/.stylelintrc
new file mode 100644
index 00000000..449f45bd
--- /dev/null
+++ b/.stylelintrc
@@ -0,0 +1,7 @@
+{
+	"extends": "stylelint-config-wikimedia",
+	"rules": {
+		"selector-no-id": null,
+		"no-descending-specificity": null
+	}
+}
diff --git a/Gruntfile.js b/Gruntfile.js
index 8d7afa41..b1905ed8 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -8,6 +8,8 @@
 module.exports = function ( grunt ) {
 	grunt.loadNpmTasks( 'grunt-jsonlint' );
 	grunt.loadNpmTasks( 'grunt-banana-checker' );
+	grunt.loadNpmTasks( 'grunt-stylelint' );
+
 	grunt.initConfig( {
 		banana: {
 			all: ['i18n/']
@@ -15,11 +17,18 @@ module.exports = function ( grunt ) {
 		jsonlint: {
 			all: [
 				'**/*.json',
+				'.stylelintrc',
+				'!node_modules/**'
+			]
+		},
+		stylelint: {
+			all: [
+				'**/*.css',
 				'!node_modules/**'
 			]
 		}
 	} );
 
-	grunt.registerTask( 'test', [ 'jsonlint', 'banana' ] );
+	grunt.registerTask( 'test', [ 'jsonlint', 'banana', 'stylelint' ] );
 	grunt.registerTask( 'default', 'test' );
 };
diff --git a/modules/ext.categoryTree.css b/modules/ext.categoryTree.css
index 21192ee6..4534123e 100644
--- a/modules/ext.categoryTree.css
+++ b/modules/ext.categoryTree.css
@@ -14,13 +14,13 @@
 }
 
 #mw-panel div.portal div.body .CategoryTreeTag {
-        margin: 0;
-        font-size: 0.75em;
-        line-height: 1.125em;
+	margin: 0;
+	font-size: 0.75em;
+	line-height: 1.125em;
 }
 
 #mw-panel div.portal div.body .CategoryTreeItem {
-        padding: 0.25em 0;
+	padding: 0.25em 0;
 }
 
 .CategoryTreeChildren {
@@ -33,7 +33,7 @@
 
 .CategoryTreeEmptyBullet {
 	cursor: default;
-	color: #C0C0C0;
+	color: #c0c0c0;
 }
 
 .CategoryTreeBullet a,
@@ -46,7 +46,7 @@
 }
 
 .CategoryTreeToggle {
-	color: #0645AD;
+	color: #0645ad;
 }
 
 .CategoryTreeLabelPage {
@@ -77,11 +77,11 @@
 	display: inline-block;
 	/* why is the -0.5ex needed? */
 	margin: -0.5ex 0 0 1ex;
-	padding:0;
+	padding: 0;
 	vertical-align: top;
 	/* IE6-7 Hack for display: inline-block */
 	zoom: 1;
-	*display: inline;
+	*display: inline; /* stylelint-disable-line declaration-block-no-duplicate-properties */
 }
 
 .CategoryTreeSection {
diff --git a/package.json b/package.json
index 7c3b0bc1..054f4109 100644
--- a/package.json
+++ b/package.json
@@ -7,9 +7,10 @@
     "test": "grunt test"
   },
   "devDependencies": {
-    "grunt": "0.4.5",
-    "grunt-cli": "0.1.13",
+    "grunt": "1.0.1",
     "grunt-banana-checker": "0.4.0",
-    "grunt-jsonlint": "1.0.7"
+    "grunt-jsonlint": "1.0.7",
+    "grunt-stylelint": "0.6.0",
+    "stylelint-config-wikimedia": "0.4.1"
   }
 }