diff --git a/src/reactA11yLangRule.ts b/src/reactA11yLangRule.ts
index e890e9563..666a107c1 100644
--- a/src/reactA11yLangRule.ts
+++ b/src/reactA11yLangRule.ts
@@ -5,7 +5,8 @@ import {ErrorTolerantWalker} from './utils/ErrorTolerantWalker';
 import {ExtendedMetadata} from './utils/ExtendedMetadata';
 import {SyntaxKind} from './utils/SyntaxKind';
 
-const FAILURE_STRING: string = 'An html element is missing the lang attribute';
+const FAILURE_MISSING_LANG: string = 'An html element is missing the lang attribute';
+const FAILURE_WRONG_LANG_CODE: string = 'Lang attribute does not have a valid value.';
 
 /**
  * Implementation of the react-a11y-lang rule.
@@ -15,7 +16,7 @@ export class Rule extends Lint.Rules.AbstractRule {
     public static metadata: ExtendedMetadata = {
         ruleName: 'react-a11y-lang',
         type: 'functionality',
-        description: '... add a meaningful one line description',
+        description: 'html element should have a valid lang attribute',
         options: null,
         issueClass: 'Ignored',
         issueType: 'Warning',
@@ -30,6 +31,19 @@ export class Rule extends Lint.Rules.AbstractRule {
 }
 
 class ReactA11yLangRuleWalker extends ErrorTolerantWalker {
+    private static languagesISO = [
+        'ab', 'aa', 'af', 'sq', 'am', 'ar', 'an', 'hy', 'as', 'ay', 'az', 'ba', 'eu', 'bn',
+        'dz', 'bh', 'bi', 'br', 'bg', 'my', 'be', 'km', 'ca', 'zh', 'zh-Hans', 'zh-Hant',
+        'co', 'hr', 'cs', 'da', 'nl', 'en', 'eo', 'et', 'fo', 'fa', 'fj', 'fi', 'fr', 'fy',
+        'gl', 'gd', 'gv', 'ka', 'de', 'el', 'kl', 'gn', 'gu', 'ht', 'ha', 'he', 'iw', 'hi',
+        'hu', 'is', 'io', 'id', 'in', 'ia', 'ie', 'iu', 'ik', 'ga', 'it', 'ja', 'jv', 'kn',
+        'ks', 'kk', 'rw', 'ky', 'rn', 'ko', 'ku', 'lo', 'la', 'lv', 'li', 'ln', 'lt', 'mk',
+        'mg', 'ms', 'ml', 'mt', 'mi', 'mr', 'mo', 'mn', 'na', 'ne', 'no', 'oc', 'or', 'om',
+        'ps', 'pl', 'pt', 'pa', 'qu', 'rm', 'ro', 'ru', 'sm', 'sg', 'sa', 'sr', 'sh', 'st',
+        'tn', 'sn', 'ii', 'sd', 'si', 'ss', 'sk', 'sl', 'so', 'es', 'su', 'sw', 'sv', 'tl',
+        'tg', 'ta', 'tt', 'te', 'th', 'bo', 'ti', 'to', 'ts', 'tr', 'tk', 'tw', 'ug', 'uk',
+        'ur', 'uz', 'vi', 'vo', 'wa', 'cy', 'wo', 'xh', 'yi', 'ji', 'yo', 'zu'
+    ];
 
     protected visitJsxSelfClosingElement(node: ts.JsxSelfClosingElement): void {
         this.validateOpeningElement(node, node);
@@ -44,16 +58,26 @@ class ReactA11yLangRuleWalker extends ErrorTolerantWalker {
     private validateOpeningElement(parent: ts.Node, openingElement: ts.JsxOpeningElement): void {
         if (openingElement.tagName.getText() === 'html') {
             const attributes: ts.NodeArray<ts.JsxAttribute | ts.JsxSpreadAttribute> = openingElement.attributes;
-            let found: boolean = false;
+            let langFound: boolean = false;
+            let validLangCode: boolean = false;
+
             attributes.forEach((attribute: ts.JsxAttribute | ts.JsxSpreadAttribute): void => {
                 if (attribute.kind === SyntaxKind.current().JsxAttribute) {
                     if ((<ts.JsxAttribute>attribute).name.getText() === 'lang') {
-                        found = true;
+                        langFound = true;
+                        let langText: string = (<ts.JsxAttribute>attribute).initializer.getText().trim();
+                        langText = langText.slice(1, -1); // 'en' ->  en
+                        if ((ReactA11yLangRuleWalker.languagesISO.indexOf(langText)) > -1) {
+                            validLangCode = true;
+                        }
                     }
                 }
             });
-            if (!found) {
-                this.addFailure(this.createFailure(parent.getStart(), parent.getWidth(), FAILURE_STRING));
+
+            if (!langFound) {
+                this.addFailure(this.createFailure(parent.getStart(), parent.getWidth(), FAILURE_MISSING_LANG));
+            } else if (!validLangCode) {
+                this.addFailure(this.createFailure(parent.getStart(), parent.getWidth(), FAILURE_WRONG_LANG_CODE));
             }
         }
     }
diff --git a/tests/ReactA11yLangRuleTests.ts b/tests/ReactA11yLangRuleTests.ts
index 34c019653..1849450ec 100644
--- a/tests/ReactA11yLangRuleTests.ts
+++ b/tests/ReactA11yLangRuleTests.ts
@@ -14,8 +14,8 @@ describe('reactA11yLangRule', () : void => {
         const script : string = `
             import React = require('react');
 
-            const x = <html lang='en'></html>;
-            const y = <html lang='en' />;
+            const x = <html lang='en' title="asdf"></html>;
+            const y = <html lang='no' />;
         `;
 
         TestHelper.assertViolations(ruleName, script, [ ]);
@@ -54,4 +54,29 @@ describe('reactA11yLangRule', () : void => {
             }
         ]);
     });
+
+    it('should fail on invalid language code', () : void => {
+        const script : string = `
+            import React = require('react');
+
+            const x = <html lang='foo'></html>;
+            const y = <html lang='bar' />;
+        `;
+
+        TestHelper.assertViolations(ruleName, script, [
+            {
+                "failure": "Lang attribute does not have a valid value.",
+                "name": "file.tsx",
+                "ruleName": "react-a11y-lang",
+                "startPosition": { "character": 23, "line": 4 }
+            },
+            {
+                "failure": "Lang attribute does not have a valid value.",
+                "name": "file.tsx",
+                "ruleName": "react-a11y-lang",
+                "startPosition": { "character": 23, "line": 5 }
+            }
+        ]);
+    });
+
 });