diff --git a/src/index.ts b/src/index.ts
index ef7637be..f24c9d21 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -25,6 +25,7 @@ import { UploadOptions } from './lib/api/upload/types';
 import { StoreUploadOptions } from './lib/api/upload';
 import { PreviewOptions } from './lib/api/preview';
 import { FilestackError } from './filestack_error';
+import { getMimetype } from './lib/utils/index';
 
 /**
  * Initialize client with given config
@@ -67,5 +68,6 @@ export {
   PickerResponse,
   Client,
   FilestackError,
-  PickerDisplayMode
+  PickerDisplayMode,
+  getMimetype
 };
diff --git a/src/lib/utils/index.ts b/src/lib/utils/index.ts
index 3c0d2d03..0d6343e0 100644
--- a/src/lib/utils/index.ts
+++ b/src/lib/utils/index.ts
@@ -136,8 +136,8 @@ export const md5 = (data: any): string => {
 export const getMimetype = (file: Uint8Array | Buffer, name?: string): string => {
   let type = fileType(file);
 
-  // check x-ms by extension
-  if (type && type.mime !== 'application/x-ms') {
+  // check x-ms and x-msi by extension
+  if (type && (type.mime !== 'application/x-ms' && type.mime !== 'application/x-msi')) {
     return type.mime;
   }