diff --git a/src/index.ts b/src/index.ts
index 54942bf..75b8a8b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -610,7 +610,7 @@ export function apply(ctx: Context, config: Config) {
             // Gets all files in the ZIP file
             const zipEntries = zip.getEntries()
             const firstImageBuffer = zip.readFile(zipEntries[0])
-            const b64 = Buffer.from(firstImageBuffer).toString('base64')
+            const b64 = firstImageBuffer.toString('base64')
             return forceDataPrefix(b64, 'image/png')
           }
           return forceDataPrefix(res.data?.trimEnd().slice(27))
diff --git a/src/utils.ts b/src/utils.ts
index a01042e..7c97433 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -21,7 +21,7 @@ export interface Size {
 
 export function getImageSize(buffer: ArrayBuffer): Size {
   if (typeof Buffer !== 'undefined') {
-    return imageSize(Buffer.from(buffer))
+    return imageSize(new Uint8Array(buffer))
   }
   const blob = new Blob([buffer])
   const image = new Image()