diff --git a/index.js b/index.js
index b9349b7..4a6e808 100644
--- a/index.js
+++ b/index.js
@@ -29,9 +29,6 @@ module.exports = attacher;
 var exists = fs.existsSync;
 var parse = url.parse;
 
-/* Constants. */
-var NS = 'remark-validate-links';
-
 /**
  * Get the `pathname` of `uri`, if applicable.
  *
@@ -89,17 +86,17 @@ function getClosest(pathname, references) {
 }
 
 /**
- * Utilitity to warn `warning` for each node in `nodes`,
+ * Utilitity to warn `reason` for each node in `nodes`,
  * on `file`.
  *
  * @param {File} file - Virtual file.
  * @param {Array.<Node>} nodes - Offending nodes.
- * @param {string} message - Message.
+ * @param {string} reason - Message.
  */
-function warnAll(file, nodes, message) {
+function warnAll(file, nodes, reason) {
   nodes.forEach(function (node) {
-    var warning = file.warn(message, node);
-    warning.source = 'remark-validate-links';
+    var message = file.message(reason, node);
+    message.source = message.ruleId = 'remark-validate-links';
   });
 }
 
@@ -117,8 +114,8 @@ function warnAll(file, nodes, message) {
  */
 function gatherReferences(file, tree, project) {
   var cache = {};
-  var filePath = file.filePath();
-  var directory = file.directory;
+  var filePath = file.path;
+  var dirname = file.dirname;
   var getDefinition;
   var prefix = '';
 
@@ -158,7 +155,7 @@ function gatherReferences(file, tree, project) {
         link = filePath + uri.hash;
         uri = parse(link);
       } else {
-        link = urljoin(directory || './', link);
+        link = urljoin(dirname, link);
         if (uri.hash) {
           link += uri.hash;
         }
@@ -238,8 +235,8 @@ function gatherReferences(file, tree, project) {
  * @param {File} file - Set of virtual files.
  */
 function validate(exposed, file) {
-  var references = file.namespace(NS).references;
-  var filePath = file.filePath();
+  var references = file.data.remarkValidateLinksReferences;
+  var filePath = file.path;
   var reference;
   var nodes;
   var real;
@@ -300,7 +297,7 @@ function completer(set, done) {
   var exposed = {};
 
   set.valueOf().forEach(function (file) {
-    var landmarks = file.namespace(NS).landmarks;
+    var landmarks = file.data.remarkValidateLinksLandmarks;
 
     if (landmarks) {
       exposed = xtend(exposed, landmarks);
@@ -309,7 +306,7 @@ function completer(set, done) {
 
   set.valueOf().forEach(function (file) {
     /* istanbul ignore else - stdin */
-    if (file.filePath()) {
+    if (file.path) {
       validate(exposed, file);
     }
   });
@@ -337,8 +334,8 @@ function transformerFactory(project, fileSet) {
    * @param {File} file - Virtual file.
    */
   function transformer(ast, file) {
-    var filePath = file.filePath();
-    var space = file.namespace(NS);
+    var filePath = file.path;
+    var space = file.data;
     var links = [];
     var landmarks = {};
     var references;
@@ -379,8 +376,8 @@ function transformerFactory(project, fileSet) {
       }
     });
 
-    space.references = references;
-    space.landmarks = landmarks;
+    space.remarkValidateLinksReferences = references;
+    space.remarkValidateLinksLandmarks = landmarks;
   }
 
   return transformer;
@@ -408,7 +405,8 @@ function attacher(remark, options, fileSet) {
    * given. */
   if (!repo) {
     try {
-      pack = require(path.resolve(process.cwd(), 'package.json'));
+      pack = fileSet.files[0].cwd;
+      pack = require(path.resolve(pack, 'package.json'));
     } catch (err) {
       pack = {};
     }
diff --git a/package.json b/package.json
index f70b264..f7dcdbe 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
     "github-url-to-object": "^2.1.0",
     "mdast-util-definitions": "^1.0.0",
     "propose": "0.0.5",
-    "remark-slug": "^4.1.0",
+    "remark-slug": "^4.2.1",
     "unist-util-visit": "^1.0.0",
     "urljoin": "^0.1.5",
     "xtend": "^4.0.1"
@@ -34,9 +34,9 @@
   ],
   "devDependencies": {
     "execa": "^0.4.0",
-    "nyc": "^7.0.0",
-    "remark": "^5.0.0",
-    "remark-cli": "^1.0.0",
+    "nyc": "^8.1.0",
+    "remark": "^6.0.0",
+    "remark-cli": "^2.0.0",
     "remark-comment-config": "^4.0.0",
     "remark-github": "^5.0.0-alpha.1",
     "remark-lint": "^4.0.0",
@@ -68,7 +68,7 @@
     "functions": 100,
     "branches": 100
   },
-  "remarkConfig": {
+  "remarkConfig-": {
     "output": true,
     "plugins": [
       "comment-config",
diff --git a/test/index.js b/test/index.js
index 389073c..852b5a5 100644
--- a/test/index.js
+++ b/test/index.js
@@ -26,6 +26,8 @@ test.onFinish(function () {
 
 var bin = path.join('..', '..', 'node_modules', '.bin', 'remark');
 
+var source = '  remark-validate-links  remark-validate-links';
+
 /* Tests. */
 test('remark-validate-links', function (t) {
   t.plan(8);
@@ -45,7 +47,7 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.',
+      '../../index',
       'definitions.md',
       'FOOOO'
     ]).catch(function (err) {
@@ -57,7 +59,7 @@ test('remark-validate-links', function (t) {
           '        1:1  error    No such file or directory',
           '',
           'definitions.md',
-          '  5:12-5:21  warning  Link to unknown heading: `world`',
+          '  5:12-5:21  warning  Link to unknown heading: `world`' + source,
           '',
           '2 messages (✖ 1 error, ⚠ 1 warning)',
           ''
@@ -74,22 +76,22 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.',
+      '../../index',
       'example.md'
     ]).then(function (stderr) {
       st.equal(
         strip(stderr),
         [
           'example.md',
-          '  5:37-5:51    warning  Link to unknown heading: `world`',
-          '  23:10-23:37  warning  Link to unknown file: `examples/world.md`',
-          '  25:10-25:35  warning  Link to unknown file: `examples/world.md`',
-          '  37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`',
-          '  39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`',
-          '  45:10-45:40  warning  Link to unknown file: `examples/world.md`',
-          '  45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`',
-          '  47:10-47:38  warning  Link to unknown file: `examples/world.md`',
-          '  47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`',
+          '    5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '  23:10-23:37  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  25:10-25:35  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '  39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '  45:10-45:40  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '  47:10-47:38  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
           '',
           '⚠ 9 warnings'
         ].join('\n'),
@@ -105,7 +107,7 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.',
+      '../../index',
       'example.md',
       'examples/example.md'
     ]).then(function (stderr) {
@@ -113,27 +115,22 @@ test('remark-validate-links', function (t) {
         strip(stderr),
         [
           'example.md',
-          '  5:37-5:51    warning  Link to unknown heading: `world`',
-          '  23:10-23:37  warning  Link to unknown file: `examples/world.md`',
-          '  25:10-25:35  warning  Link to unknown file: `examples/world.md`',
-          '  37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`',
-          '  39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`',
-          '  45:10-45:40  warning  Link to unknown file: `examples/world.md`',
-          '  45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`',
-          '  47:10-47:38  warning  Link to unknown file: `examples/world.md`',
-          '  47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`',
+          '    5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '  23:10-23:37  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  25:10-25:35  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '  39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '  45:10-45:40  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '  47:10-47:38  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '  47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
           '',
           'examples/example.md',
-          '  5:37-5:51    warning  Link to unknown heading: ' +
-            '`world`',
-          '  19:10-19:29  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  29:10-29:34  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  35:10-35:32  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  35:10-35:32  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
+          '    5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '  19:10-19:29  warning  Link to unknown file: `world.md`                         ' + source,
+          '  29:10-29:34  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '  35:10-35:32  warning  Link to unknown file: `world.md`                         ' + source,
+          '  35:10-35:32  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
           '',
           '⚠ 14 warnings'
         ].join('\n'),
@@ -149,14 +146,14 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.',
+      '../../index',
       'definitions.md'
     ]).then(function (stderr) {
       st.equal(
         strip(stderr),
         [
           'definitions.md',
-          '  5:12-5:21  warning  Link to unknown heading: `world`',
+          '  5:12-5:21  warning  Link to unknown heading: `world`' + source,
           '',
           '⚠ 1 warning'
         ].join('\n'),
@@ -172,7 +169,7 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.=repository:"wooorm/test"',
+      '../../index=repository:"wooorm/test"',
       'example.md',
       'examples/example.md'
     ]).then(function (stderr) {
@@ -180,68 +177,38 @@ test('remark-validate-links', function (t) {
         strip(stderr),
         [
           'example.md',
-          '  5:37-5:51     warning  Link to unknown heading: ' +
-            '`world`',
-          '  19:34-19:102  warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  21:12-21:81   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  23:10-23:37   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  25:10-25:35   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  37:10-37:42   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  39:10-39:40   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  41:10-41:83   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  43:10-43:84   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  45:10-45:40   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  45:10-45:40   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  47:10-47:38   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  47:10-47:38   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  49:10-49:81   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  49:10-49:81   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  51:10-51:82   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  51:10-51:82   warning  Link to unknown file: ' +
-            '`examples/world.md`',
+          '     5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '  19:34-19:102  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   21:12-21:81  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   23:10-23:37  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   25:10-25:35  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   41:10-41:83  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   43:10-43:84  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   45:10-45:40  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   47:10-47:38  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   49:10-49:81  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   49:10-49:81  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   51:10-51:82  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   51:10-51:82  warning  Link to unknown file: `examples/world.md`                ' + source,
           '',
           'examples/example.md',
-          '  5:37-5:51    warning  Link to unknown heading: ' +
-            '`world`',
-          '  15:34-15:93  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  17:12-17:72  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  19:10-19:29  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  29:10-29:34  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  31:10-31:74  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  33:10-33:75  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  35:10-35:32  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  35:10-35:32  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  37:10-37:72  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  37:10-37:72  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  39:10-39:73  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  39:10-39:73  warning  Link to unknown file: ' +
-            '`world.md`',
+          '     5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '   15:34-15:93  warning  Link to unknown file: `world.md`                         ' + source,
+          '   17:12-17:72  warning  Link to unknown file: `world.md`                         ' + source,
+          '   19:10-19:29  warning  Link to unknown file: `world.md`                         ' + source,
+          '   29:10-29:34  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   31:10-31:74  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   33:10-33:75  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   35:10-35:32  warning  Link to unknown file: `world.md`                         ' + source,
+          '   35:10-35:32  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   37:10-37:72  warning  Link to unknown file: `world.md`                         ' + source,
+          '   37:10-37:72  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   39:10-39:73  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   39:10-39:73  warning  Link to unknown file: `world.md`                         ' + source,
           '',
           '⚠ 30 warnings'
         ].join('\n'),
@@ -275,68 +242,38 @@ test('remark-validate-links', function (t) {
         strip(stderr),
         [
           'example.md',
-          '  5:37-5:51     warning  Link to unknown heading: ' +
-            '`world`',
-          '  19:34-19:102  warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  21:12-21:81   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  23:10-23:37   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  25:10-25:35   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  37:10-37:42   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  39:10-39:40   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  41:10-41:83   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  43:10-43:84   warning  Link to unknown heading in ' +
-            '`examples/example.md`: `world`',
-          '  45:10-45:40   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  45:10-45:40   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  47:10-47:38   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  47:10-47:38   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  49:10-49:81   warning  Link to unknown file: ' +
-            '`examples/world.md`',
-          '  49:10-49:81   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  51:10-51:82   warning  Link to unknown heading in ' +
-            '`examples/world.md`: `hello`',
-          '  51:10-51:82   warning  Link to unknown file: ' +
-            '`examples/world.md`',
+          '     5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '  19:34-19:102  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   21:12-21:81  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   23:10-23:37  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   25:10-25:35  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   37:10-37:42  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   39:10-39:40  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   41:10-41:83  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   43:10-43:84  warning  Link to unknown heading in `examples/example.md`: `world`' + source,
+          '   45:10-45:40  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   45:10-45:40  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   47:10-47:38  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   47:10-47:38  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   49:10-49:81  warning  Link to unknown file: `examples/world.md`                ' + source,
+          '   49:10-49:81  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   51:10-51:82  warning  Link to unknown heading in `examples/world.md`: `hello`  ' + source,
+          '   51:10-51:82  warning  Link to unknown file: `examples/world.md`                ' + source,
           '',
           'examples/example.md',
-          '  5:37-5:51    warning  Link to unknown heading: ' +
-            '`world`',
-          '  15:34-15:93  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  17:12-17:72  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  19:10-19:29  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  29:10-29:34  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  31:10-31:74  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  33:10-33:75  warning  Link to unknown heading in ' +
-            '`example.md`: `world`',
-          '  35:10-35:32  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  35:10-35:32  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  37:10-37:72  warning  Link to unknown file: ' +
-            '`world.md`',
-          '  37:10-37:72  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  39:10-39:73  warning  Link to unknown heading in ' +
-            '`world.md`: `hello`',
-          '  39:10-39:73  warning  Link to unknown file: ' +
-            '`world.md`',
+          '     5:37-5:51  warning  Link to unknown heading: `world`                         ' + source,
+          '   15:34-15:93  warning  Link to unknown file: `world.md`                         ' + source,
+          '   17:12-17:72  warning  Link to unknown file: `world.md`                         ' + source,
+          '   19:10-19:29  warning  Link to unknown file: `world.md`                         ' + source,
+          '   29:10-29:34  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   31:10-31:74  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   33:10-33:75  warning  Link to unknown heading in `example.md`: `world`         ' + source,
+          '   35:10-35:32  warning  Link to unknown file: `world.md`                         ' + source,
+          '   35:10-35:32  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   37:10-37:72  warning  Link to unknown file: `world.md`                         ' + source,
+          '   37:10-37:72  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   39:10-39:73  warning  Link to unknown heading in `world.md`: `hello`           ' + source,
+          '   39:10-39:73  warning  Link to unknown file: `world.md`                         ' + source,
           '',
           '⚠ 30 warnings'
         ].join('\n'),
@@ -352,17 +289,15 @@ test('remark-validate-links', function (t) {
       '--no-config',
       '--no-ignore',
       '--use',
-      '.',
+      '../../index',
       'suggestions.md'
     ]).then(function (stderr) {
       st.equal(
         strip(stderr),
         [
           'suggestions.md',
-          '  3:22-3:37  warning  Link to unknown heading: ' +
-            '`helloo`. Did you mean `hello`',
-          '  7:17-7:40  warning  Link to unknown heading in ' +
-            '`example.md`: `fiiiles`. Did you mean `files`',
+          '  3:22-3:37  warning  Link to unknown heading: `helloo`. Did you mean `hello`                 ' + source,
+          '  7:17-7:40  warning  Link to unknown heading in `example.md`: `fiiiles`. Did you mean `files`' + source,
           '',
           '⚠ 2 warnings'
         ].join('\n'),