diff --git a/src/Document.js b/src/Document.js
index 6f6066a..e8befaa 100644
--- a/src/Document.js
+++ b/src/Document.js
@@ -1,5 +1,3 @@
-/* eslint-disable no-dupe-class-members */
-
 const libxmljs = require('libxmljs');
 const utils = require('./utils');
 
@@ -64,11 +62,7 @@
     return this._original.childNodes();
   }
 
-  encoding() {
-    return this._original.encoding();
-  }
-
-  encoding(enc) {
+  encoding(enc = null) {
     return this._original.encoding(enc);
   }
 
@@ -141,13 +135,7 @@
     return this._original.rngValidate(rng);
   }
 
-  root() {
-    this.assertNoContentError();
-
-    return this._original.root();
-  }
-
-  root(node) {
+  root(node = null) {
     this.assertNoContentError();
 
     return this._original.root(node);
@@ -157,6 +145,17 @@
     return this._original.setDtd(name, ext, sys);
   }
 
+  setNamespace(alias, url) {
+    if (typeof alias !== 'string') throw new Error('alias must be a string.');
+    if (typeof url !== 'string') throw new Error('url must be a string.');
+    if (!utils.isValidURL(url)) throw new Error('url is not a valid URL.');
+
+    this.namespace = {
+      alias,
+      url,
+    };
+  }
+
   toString(formatting = true) {
     return this._original.toString(formatting);
   }