diff --git a/create-or-update-files.js b/create-or-update-files.js
index 0eef604..838597f 100644
--- a/create-or-update-files.js
+++ b/create-or-update-files.js
@@ -1,14 +1,23 @@
 function isBase64(str) {
+  // Handle buffer inputs
+  if (Buffer.isBuffer(str)) {
+    str = str.toString("utf8");
+  }
+
   var notBase64 = /[^A-Z0-9+\/=]/i;
-  const isString = (typeof str === 'string' || str instanceof String);
+  const isString = typeof str === "string" || str instanceof String;
 
   if (!isString) {
     let invalidType;
     if (str === null) {
-      invalidType = 'null';
+      invalidType = "null";
     } else {
       invalidType = typeof str;
-      if (invalidType === 'object' && str.constructor && str.constructor.hasOwnProperty('name')) {
+      if (
+        invalidType === "object" &&
+        str.constructor &&
+        str.constructor.hasOwnProperty("name")
+      ) {
         invalidType = str.constructor.name;
       } else {
         invalidType = `a ${invalidType}`;
@@ -21,10 +30,12 @@ function isBase64(str) {
   if (!len || len % 4 !== 0 || notBase64.test(str)) {
     return false;
   }
-  const firstPaddingChar = str.indexOf('=');
-  return firstPaddingChar === -1 ||
+  const firstPaddingChar = str.indexOf("=");
+  return (
+    firstPaddingChar === -1 ||
     firstPaddingChar === len - 1 ||
-    (firstPaddingChar === len - 2 && str[len - 1] === '=');
+    (firstPaddingChar === len - 2 && str[len - 1] === "=")
+  );
 }
 
 module.exports = function (octokit, opts) {
diff --git a/create-or-update-files.test.js b/create-or-update-files.test.js
index 9d63692..69ffe07 100644
--- a/create-or-update-files.test.js
+++ b/create-or-update-files.test.js
@@ -235,6 +235,36 @@ test(`success (base64 encoded body)`, async () => {
   await expect(run(body)).resolves.toEqual(mockCommitList);
 });
 
+test(`success (buffer body provided)`, async () => {
+  const body = {
+    ...validRequest,
+    changes: [
+      {
+        message: "Your commit message",
+        files: {
+          "test.md": Buffer.from(
+            `# This is a test
+
+I hope it works`,
+          ),
+          "test2.md": {
+            contents: `Something else`,
+          },
+        },
+      },
+    ],
+  };
+
+  mockGetRef(branch, `sha-${branch}`, true);
+  mockCreateBlobFileOne();
+  mockCreateBlobFileTwo();
+  mockCreateTree(`sha-${branch}`);
+  mockCommit(`sha-${branch}`);
+  mockUpdateRef(branch);
+
+  await expect(run(body)).resolves.toEqual(mockCommitList);
+});
+
 test(`success (committer details)`, async () => {
   const committer = {
     name: "Ashley Person",