diff --git a/ts/types/Attachment.ts b/ts/types/Attachment.ts
index d37b2f3e341..fccc9962d49 100644
--- a/ts/types/Attachment.ts
+++ b/ts/types/Attachment.ts
@@ -4,11 +4,11 @@ import moment from 'moment';
 import * as GoogleChrome from '../util/GoogleChrome';
 import { saveURLAsFile } from '../util/saveURLAsFile';
 import { arrayBufferToObjectURL } from '../util/arrayBufferToObjectURL';
-import { MIMEType } from './MIME';
+import * as MIME from './MIME';
 
 export type Attachment = {
   fileName?: string;
-  contentType?: MIMEType;
+  contentType?: MIME.MIMEType;
   size?: number;
   data: ArrayBuffer;
 
@@ -27,8 +27,6 @@ interface AttachmentSchemaVersion3 {
   path: string;
 }
 
-const SAVE_CONTENT_TYPE = 'application/octet-stream' as MIMEType;
-
 export const isVisualMedia = (attachment: Attachment): boolean => {
   const { contentType } = attachment;
 
@@ -57,7 +55,7 @@ export const save = ({
     ? getAbsolutePath(attachment.path)
     : arrayBufferToObjectURL({
         data: attachment.data,
-        type: SAVE_CONTENT_TYPE,
+        type: MIME.APPLICATION_OCTET_STREAM,
       });
   const filename = getSuggestedFilename({ attachment, timestamp });
   saveURLAsFile({ url, filename, document });
diff --git a/ts/types/MIME.ts b/ts/types/MIME.ts
index 620df41c96a..43ed14efb05 100644
--- a/ts/types/MIME.ts
+++ b/ts/types/MIME.ts
@@ -4,3 +4,5 @@ export const isJPEG = (value: MIMEType): boolean => value === 'image/jpeg';
 export const isImage = (value: MIMEType): boolean => value.startsWith('image/');
 export const isVideo = (value: MIMEType): boolean => value.startsWith('video/');
 export const isAudio = (value: MIMEType): boolean => value.startsWith('audio/');
+
+export const APPLICATION_OCTET_STREAM = 'application/octet-stream' as MIMEType;