diff --git a/README.md b/README.md
index 7ba1456..45b1337 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,8 @@ steps:
   with:
     version: '10.x'
     registry-url: <registry url>
-- run: npm install
+- run: npm install -g yarn
+- run: yarn install
 - run: yarn publish
   env:
     NODE_AUTH_TOKEN: ${{ secrets.YARN_TOKEN }}
diff --git a/lib/authutil.js b/lib/authutil.js
index bae941b..f1a978d 100644
--- a/lib/authutil.js
+++ b/lib/authutil.js
@@ -11,13 +11,11 @@ const fs = __importStar(require("fs"));
 const os = __importStar(require("os"));
 const path = __importStar(require("path"));
 const core = __importStar(require("@actions/core"));
-function configAuth(registryUrl) {
-    let npmrc = path.resolve(process.cwd(), '.npmrc');
-    let yarnrc = path.resolve(process.cwd(), '.yarnrc');
+function configAuthentication(registryUrl) {
+    const npmrc = path.resolve(process.cwd(), '.npmrc');
     writeRegistryToFile(registryUrl, npmrc);
-    writeRegistryToFile(registryUrl, yarnrc);
 }
-exports.configAuth = configAuth;
+exports.configAuthentication = configAuthentication;
 function writeRegistryToFile(registryUrl, fileLocation) {
     core.debug(`Setting auth in ${fileLocation}`);
     let newContents = '';
@@ -25,7 +23,7 @@ function writeRegistryToFile(registryUrl, fileLocation) {
         const curContents = fs.readFileSync(fileLocation, 'utf8');
         curContents.split(os.EOL).forEach((line) => {
             // Add current contents unless they are setting the registry
-            if (!line.startsWith('registry')) {
+            if (!line.toLowerCase().startsWith('registry')) {
                 newContents += line + os.EOL;
             }
         });
@@ -36,7 +34,7 @@ function writeRegistryToFile(registryUrl, fileLocation) {
             os.EOL +
             'always-auth=true' +
             os.EOL +
-            registryUrl.replace(/(^\w+:|^)/, '') +
+            registryUrl.replace(/(^\w+:|^)/, '') + // Remove http: or https: from front of registry.
             ':_authToken=${NODE_AUTH_TOKEN}';
     fs.writeFileSync(fileLocation, newContents);
 }
diff --git a/lib/setup-node.js b/lib/setup-node.js
index 26d716a..974936f 100644
--- a/lib/setup-node.js
+++ b/lib/setup-node.js
@@ -33,7 +33,7 @@ function run() {
             }
             const registryUrl = core.getInput('registry-url');
             if (registryUrl) {
-                auth.configAuth(registryUrl);
+                auth.configAuthentication(registryUrl);
             }
             // TODO: setup proxy from runner proxy config
             const matchersPath = path.join(__dirname, '..', '.github');
diff --git a/src/authutil.ts b/src/authutil.ts
index bcd1f87..99cb33b 100644
--- a/src/authutil.ts
+++ b/src/authutil.ts
@@ -3,22 +3,20 @@ import * as os from 'os';
 import * as path from 'path';
 import * as core from '@actions/core';
 
-export function configAuth(registryUrl: string) {
-  let npmrc: string = path.resolve(process.cwd(), '.npmrc');
-  let yarnrc: string = path.resolve(process.cwd(), '.yarnrc');
+export function configAuthentication(registryUrl: string) {
+  const npmrc: string = path.resolve(process.cwd(), '.npmrc');
 
   writeRegistryToFile(registryUrl, npmrc);
-  writeRegistryToFile(registryUrl, yarnrc);
 }
 
 function writeRegistryToFile(registryUrl: string, fileLocation: string) {
   core.debug(`Setting auth in ${fileLocation}`);
   let newContents = '';
   if (fs.existsSync(fileLocation)) {
-    const curContents = fs.readFileSync(fileLocation, 'utf8');
+    const curContents: string = fs.readFileSync(fileLocation, 'utf8');
     curContents.split(os.EOL).forEach((line: string) => {
       // Add current contents unless they are setting the registry
-      if (!line.startsWith('registry')) {
+      if (!line.toLowerCase().startsWith('registry')) {
         newContents += line + os.EOL;
       }
     });
@@ -29,7 +27,7 @@ function writeRegistryToFile(registryUrl: string, fileLocation: string) {
     os.EOL +
     'always-auth=true' +
     os.EOL +
-    registryUrl.replace(/(^\w+:|^)/, '') +
+    registryUrl.replace(/(^\w+:|^)/, '') + // Remove http: or https: from front of registry.
     ':_authToken=${NODE_AUTH_TOKEN}';
   fs.writeFileSync(fileLocation, newContents);
 }
diff --git a/src/setup-node.ts b/src/setup-node.ts
index c038786..ba64e24 100644
--- a/src/setup-node.ts
+++ b/src/setup-node.ts
@@ -15,9 +15,9 @@ async function run() {
       await installer.getNode(version);
     }
 
-    const registryUrl = core.getInput('registry-url');
+    const registryUrl: string = core.getInput('registry-url');
     if (registryUrl) {
-      auth.configAuth(registryUrl);
+      auth.configAuthentication(registryUrl);
     }
 
     // TODO: setup proxy from runner proxy config