diff --git a/types/commonmark/commonmark-tests.ts b/types/commonmark/commonmark-tests.ts
index d298972f89..8d3a3a5447 100644
--- a/types/commonmark/commonmark-tests.ts
+++ b/types/commonmark/commonmark-tests.ts
@@ -1,9 +1,6 @@
-
-
 import commonmark = require('commonmark');
 
 function logNode(node: commonmark.Node) {
-
     console.log(
         node.destination,
         node.firstChild,
@@ -24,12 +21,10 @@ function logNode(node: commonmark.Node) {
         node.sourcepos,
         node.title,
         node.type);
-
 }
 
-var parser = new commonmark.Parser({ smart: true, time: true });
-var node = parser.parse('# a piece of _markdown_');
-
+const parser = new commonmark.Parser({ smart: true, time: true });
+const node = parser.parse('# a piece of _markdown_');
 
 let w = node.walker();
 let step = w.next();
@@ -37,11 +32,75 @@ if (step.entering) {
     logNode(step.node);
 }
 
-
 let xmlRenderer = new commonmark.XmlRenderer({ sourcepos: true, time: true });
 let xml = xmlRenderer.render(node);
 console.log(xml);
 
-let htmlRenderer = new commonmark.HtmlRenderer({ safe: true, smart: true, sourcepos: true, time: true});
+let htmlRenderer = new commonmark.HtmlRenderer({ safe: true, smart: true, sourcepos: true, time: true });
 let html = htmlRenderer.render(node);
-console.log(html);
\ No newline at end of file
+console.log(html);
+
+function basic_usage() {
+    const reader = new commonmark.Parser();
+    const writer = new commonmark.HtmlRenderer();
+    const parsed = reader.parse('Hello *world*'); // parsed is a 'Node' tree
+    // transform parsed if you like...
+    const result = writer.render(parsed); // result is a String
+}
+
+function constructor_optional_options() {
+    const writer = new commonmark.HtmlRenderer({ sourcepos: true });
+}
+
+function soft_breaks_as_hard_breaks() {
+    const writer = new commonmark.HtmlRenderer();
+    writer.softbreak = '<br />';
+}
+
+function soft_breaks_as_spaces() {
+    const writer = new commonmark.HtmlRenderer();
+    writer.softbreak = ' ';
+}
+
+function text_to_ALL_CAPS(parsed: commonmark.Node) {
+    const walker = parsed.walker();
+    let event: commonmark.NodeWalkingStep;
+    let node: commonmark.Node;
+
+    event = walker.next();
+    while (event) {
+        node = event.node;
+        if (event.entering && node.type === 'text') {
+            node.literal = node.literal!.toUpperCase();
+        }
+        event = walker.next();
+    }
+}
+
+function emphasis_to_ALL_CAPS(parsed: commonmark.Node) {
+    const walker = parsed.walker();
+    let event: commonmark.NodeWalkingStep;
+    let node: commonmark.Node;
+    let inEmph = false;
+
+    event = walker.next();
+    while (event) {
+        node = event.node;
+        if (node.type === 'emph') {
+            if (event.entering) {
+                inEmph = true;
+            } else {
+                inEmph = false;
+                // add Emph node's children as siblings
+                while (node.firstChild) {
+                    node.insertBefore(node.firstChild);
+                }
+                // remove the empty Emph node
+                node.unlink();
+            }
+        } else if (inEmph && node.type === 'text') {
+            node.literal = node.literal!.toUpperCase();
+        }
+        event = walker.next();
+    }
+}
diff --git a/types/commonmark/index.d.ts b/types/commonmark/index.d.ts
index bba8cd7e36..d9ce80b1a5 100644
--- a/types/commonmark/index.d.ts
+++ b/types/commonmark/index.d.ts
@@ -1,212 +1,221 @@
-// Type definitions for commonmark.js 0.22.1
+// Type definitions for commonmark.js 0.27
 // Project: https://github.com/jgm/commonmark.js
 // Definitions by: Nico Jansen <https://github.com/nicojs>
+//                 Leonard Thieu <https://github.com/leonard-thieu>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
-export = commonmark;
-export as namespace commonmark;
-
-declare namespace commonmark {
-
-    export interface NodeWalkingStep {
-        /**
-         * a boolean, which is true when we enter a Node from a parent or sibling, and false when we reenter it from a child
-         */
-        entering: boolean;
-        /**
-         * The node belonging to this step
-         */
-        node: Node;
-    }
-
-    export interface NodeWalker {
-        /**
-         * Returns an object with properties entering and node. Returns null when we have finished walking the tree.
-         */
-        next(): NodeWalkingStep;
-        /**
-         * Resets the iterator to resume at the specified node and setting for entering. (Normally this isn't needed unless you do destructive updates to the Node tree.)
-         */
-        resumeAt(node: Node, entering?: boolean): void;
-    }
-
-    export interface Position extends Array<Array<number>> {
-    }
-
-    export interface ListData {
-        type?: string,
-        tight?: boolean,
-        delimiter?: string,
-        bulletChar?: string
-    }
-
-    export class Node {
-        constructor(nodeType: string, sourcepos?: Position);
-        isContainer: boolean;
-
-        /**
-         * (read-only): one of Text, Softbreak, Hardbreak, Emph, Strong, Html, Link, Image, Code, Document, Paragraph, BlockQuote, Item, List, Heading, CodeBlock, HtmlBlock ThematicBreak.
-         */
-        type: string;
-        /**
-         * (read-only): a Node or null.
-         */
-        firstChild: Node;
-        /**
-         * (read-only): a Node or null.
-         */
-        lastChild: Node;
-        /**
-         * (read-only): a Node or null.
-         */
-        next: Node;
-        /**
-         * (read-only): a Node or null.
-         */
-        prev: Node;
-        /**
-         * (read-only): a Node or null.
-         */
-        parent: Node;
-        /**
-         * (read-only): an Array with the following form: [[startline, startcolumn], [endline, endcolumn]]
-         */
-        sourcepos: Position;
-        /**
-         *  the literal String content of the node or null.
-         */
-        literal: string;
-        /**
-         * link or image destination (String) or null.
-         */
-        destination: string;
-        /**
-         *  link or image title (String) or null.
-         */
-        title: string;
-        /**
-         * fenced code block info string (String) or null.
-         */
-        info: string;
-        /**
-         * heading level (Number).
-         */
-        level: number;
-        /**
-         * either Bullet or Ordered (or undefined).
-         */
-        listType: string;
-        /**
-         * true if list is tight
-         */
-        listTight: boolean;
-        /**
-         * a Number, the starting number of an ordered list.
-         */
-        listStart: number;
-        /**
-         * a String, either ) or . for an ordered list.
-         */
-        listDelimiter: string;
-        /**
-         * used only for CustomBlock or CustomInline.
-         */
-        onEnter: string;
-        /**
-         * used only for CustomBlock or CustomInline.
-         */
-        onExit: string;
-        /**
-         * Append a Node child to the end of the Node's children.
-         */
-        appendChild(child: Node): void;
-        /**
-         *  Prepend a Node child to the beginning of the Node's children.
-         */
-        prependChild(child: Node): void;
-        /**
-         *  Remove the Node from the tree, severing its links with siblings and parents, and closing up gaps as needed.
-         */
-        unlink(): void;
-        /**
-         * Insert a Node sibling after the Node.
-         */
-        insertAfter(sibling: Node): void;
-        /**
-         * Insert a Node sibling before the Node.
-         */
-        insertBefore(sibling: Node): void;
-        /**
-         * Returns a NodeWalker that can be used to iterate through the Node tree rooted in the Node
-         */
-        walker(): NodeWalker;
-        /**
-         * Setting the backing object of listType, listTight, listStat and listDelimiter directly.
-         * Not needed unless creating list nodes directly. Should be fixed from v>0.22.1
-         * https://github.com/jgm/commonmark.js/issues/74
-         */
-        _listData: ListData;
-    }
+export class Node {
+    constructor(nodeType: string, sourcepos?: Position);
 
     /**
-     * Instead of converting Markdown directly to HTML, as most converters do, commonmark.js parses Markdown to an AST (abstract syntax tree), and then renders this AST as HTML.
-     * This opens up the possibility of manipulating the AST between parsing and rendering. For example, one could transform emphasis into ALL CAPS.
+     * (read-only): a String, one of text, softbreak, linebreak, emph, strong, html_inline, link, image, code, document, paragraph,
+     * block_quote, item, list, heading, code_block, html_block, thematic_break.
      */
-    export class Parser {
-        /**
-         * Constructs a new Parser
-         */
-        constructor(options?: ParserOptions);
-        parse(input: string): Node;
-    }
+    readonly type: 'text' | 'softbreak' | 'linebreak' | 'emph' | 'strong' | 'html_inline' | 'link' | 'image' | 'code' | 'document' |
+        'paragraph' | 'block_quote' | 'item' | 'list' | 'heading' | 'code_block' | 'html_block' | 'thematic_break';
+    /**
+     * (read-only): a Node or null.
+     */
+    readonly firstChild: Node | null;
+    /**
+     * (read-only): a Node or null.
+     */
+    readonly lastChild: Node | null;
+    /**
+     * (read-only): a Node or null.
+     */
+    readonly next: Node | null;
+    /**
+     * (read-only): a Node or null.
+     */
+    readonly prev: Node | null;
+    /**
+     * (read-only): a Node or null.
+     */
+    readonly parent: Node | null;
+    /**
+     * (read-only): an Array with the following form: [[startline, startcolumn], [endline, endcolumn]]
+     */
+    readonly sourcepos: Position;
+    /**
+     * (read-only): true if the Node can contain other Nodes as children.
+     */
+    readonly isContainer: boolean;
+    /**
+     *  the literal String content of the node or null.
+     */
+    literal: string | null;
+    /**
+     * link or image destination (String) or null.
+     */
+    destination: string | null;
+    /**
+     *  link or image title (String) or null.
+     */
+    title: string | null;
+    /**
+     * fenced code block info string (String) or null.
+     */
+    info: string | null;
+    /**
+     * heading level (Number).
+     */
+    level: number;
+    /**
+     * either Bullet or Ordered (or undefined).
+     */
+    listType: 'Bullet' | 'Ordered';
+    /**
+     * true if list is tight
+     */
+    listTight: boolean;
+    /**
+     * a Number, the starting number of an ordered list.
+     */
+    listStart: number;
+    /**
+     * a String, either ) or . for an ordered list.
+     */
+    listDelimiter: ')' | '.';
+    /**
+     * used only for CustomBlock or CustomInline.
+     */
+    onEnter: string;
+    /**
+     * used only for CustomBlock or CustomInline.
+     */
+    onExit: string;
 
-    export interface ParserOptions {
-        /**
-         *  if true, straight quotes will be made curly, -- will be changed to an en dash, --- will be changed to an em dash, and ... will be changed to ellipses.
-         */
-        smart?: boolean;
-        time?: boolean;
-    }
+    /**
+     * Append a Node child to the end of the Node's children.
+     */
+    appendChild(child: Node): void;
 
-    export interface HtmlRenderingOptions extends XmlRenderingOptions {
-        /**
-         *  if true, raw HTML will not be passed through to HTML output (it will be replaced by comments), and potentially unsafe URLs in links and images (those beginning with javascript:, vbscript:, file:, and with a few exceptions data:) will be replaced with empty strings.
-         */
-        safe?: boolean;
-        /**
-         *  if true, straight quotes will be made curly, -- will be changed to an en dash, --- will be changed to an em dash, and ... will be changed to ellipses.
-         */
-        smart?: boolean;
-        /**
-         *  if true, source position information for block-level elements will be rendered in the data-sourcepos attribute (for HTML) or the sourcepos attribute (for XML).
-         */
-        sourcepos?: boolean;
-    }
+    /**
+     *  Prepend a Node child to the beginning of the Node's children.
+     */
+    prependChild(child: Node): void;
 
-    export class HtmlRenderer {
-        constructor(options?: HtmlRenderingOptions)
-        render(root: Node): string;
-        /**
-         * Let's you override the softbreak properties of a renderer. So, to make soft breaks render as hard breaks in HTML:
-         * writer.softbreak = "<br />";
-         */
-        softbreak: string;
-        /**
-         * Override the function that will be used to escape (sanitize) the html output. Return value is used to add to the html output
-         * @param input the input to escape
-         * @param isAttributeValue indicates wheter or not the input value will be used as value of an html attribute.
-         */
-        escape: (input: string, isAttributeValue: boolean) => string;
-    }
+    /**
+     *  Remove the Node from the tree, severing its links with siblings and parents, and closing up gaps as needed.
+     */
+    unlink(): void;
 
-    export interface XmlRenderingOptions {
-        time?: boolean;
-        sourcepos?: boolean;
-    }
+    /**
+     * Insert a Node sibling after the Node.
+     */
+    insertAfter(sibling: Node): void;
 
-    export class XmlRenderer {
-        constructor(options?: XmlRenderingOptions)
-        render(root: Node): string;
-    }
+    /**
+     * Insert a Node sibling before the Node.
+     */
+    insertBefore(sibling: Node): void;
 
+    /**
+     * Returns a NodeWalker that can be used to iterate through the Node tree rooted in the Node
+     */
+    walker(): NodeWalker;
+
+    /**
+     * Setting the backing object of listType, listTight, listStat and listDelimiter directly.
+     * Not needed unless creating list nodes directly. Should be fixed from v>0.22.1
+     * https://github.com/jgm/commonmark.js/issues/74
+     */
+    _listData: ListData;
+}
+
+/**
+ * Instead of converting Markdown directly to HTML, as most converters do, commonmark.js parses Markdown to an AST (abstract syntax tree), and then renders this AST as HTML.
+ * This opens up the possibility of manipulating the AST between parsing and rendering. For example, one could transform emphasis into ALL CAPS.
+ */
+export class Parser {
+    /**
+     * Constructs a new Parser
+     */
+    constructor(options?: ParserOptions);
+
+    parse(input: string): Node;
+}
+
+export class HtmlRenderer {
+    constructor(options?: HtmlRenderingOptions)
+
+    render(root: Node): string;
+
+    /**
+     * Let's you override the softbreak properties of a renderer. So, to make soft breaks render as hard breaks in HTML:
+     * writer.softbreak = "<br />";
+     */
+    softbreak: string;
+    /**
+     * Override the function that will be used to escape (sanitize) the html output. Return value is used to add to the html output
+     * @param input the input to escape
+     * @param isAttributeValue indicates wheter or not the input value will be used as value of an html attribute.
+     */
+    escape: (input: string, isAttributeValue: boolean) => string;
+}
+
+export class XmlRenderer {
+    constructor(options?: XmlRenderingOptions)
+
+    render(root: Node): string;
+}
+export interface NodeWalkingStep {
+    /**
+     * a boolean, which is true when we enter a Node from a parent or sibling, and false when we reenter it from a child
+     */
+    entering: boolean;
+    /**
+     * The node belonging to this step
+     */
+    node: Node;
+}
+
+export interface NodeWalker {
+    /**
+     * Returns an object with properties entering and node. Returns null when we have finished walking the tree.
+     */
+    next(): NodeWalkingStep;
+    /**
+     * Resets the iterator to resume at the specified node and setting for entering. (Normally this isn't needed unless you do destructive updates to the Node tree.)
+     */
+    resumeAt(node: Node, entering?: boolean): void;
+}
+
+export type Position = [[number, number], [number, number]];
+
+export interface ListData {
+    type?: string;
+    tight?: boolean;
+    delimiter?: string;
+    bulletChar?: string;
+}
+
+export interface ParserOptions {
+    /**
+     *  if true, straight quotes will be made curly, -- will be changed to an en dash, --- will be changed to an em dash, and ... will be changed to ellipses.
+     */
+    smart?: boolean;
+    time?: boolean;
+}
+
+export interface HtmlRenderingOptions extends XmlRenderingOptions {
+    /**
+     *  if true, raw HTML will not be passed through to HTML output (it will be replaced by comments), and potentially unsafe URLs in links and images
+     *  (those beginning with javascript:, vbscript:, file:, and with a few exceptions data:) will be replaced with empty strings.
+     */
+    safe?: boolean;
+    /**
+     *  if true, straight quotes will be made curly, -- will be changed to an en dash, --- will be changed to an em dash, and ... will be changed to ellipses.
+     */
+    smart?: boolean;
+    /**
+     *  if true, source position information for block-level elements will be rendered in the data-sourcepos attribute (for HTML) or the sourcepos attribute (for XML).
+     */
+    sourcepos?: boolean;
+}
+
+export interface XmlRenderingOptions {
+    time?: boolean;
+    sourcepos?: boolean;
 }
diff --git a/types/commonmark/tsconfig.json b/types/commonmark/tsconfig.json
index e424e972ca..82e3004b78 100644
--- a/types/commonmark/tsconfig.json
+++ b/types/commonmark/tsconfig.json
@@ -7,7 +7,7 @@
         ],
         "noImplicitAny": true,
         "noImplicitThis": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "baseUrl": "../",
         "typeRoots": [
             "../"
@@ -20,4 +20,4 @@
         "index.d.ts",
         "commonmark-tests.ts"
     ]
-}
\ No newline at end of file
+}
diff --git a/types/commonmark/tslint.json b/types/commonmark/tslint.json
new file mode 100644
index 0000000000..f93cf8562a
--- /dev/null
+++ b/types/commonmark/tslint.json
@@ -0,0 +1,3 @@
+{
+    "extends": "dtslint/dt.json"
+}