diff --git a/server/objects/Download.js b/server/objects/Download.js
index 542e0ef7..5baa3367 100644
--- a/server/objects/Download.js
+++ b/server/objects/Download.js
@@ -1,5 +1,8 @@
+const { AudioMimeType } = require('../utils/constants')
+const { getAudioMimeTypeFromExtname } = require('../utils/fileUtils')
 const DEFAULT_EXPIRATION = 1000 * 60 * 60 // 60 minutes
 const DEFAULT_TIMEOUT = 1000 * 60 * 30 // 30 minutes
+
 class Download {
   constructor(download) {
     this.id = null
@@ -32,16 +35,7 @@ class Download {
   }
 
   get mimeType() {
-    if (this.ext === '.mp3' || this.ext === '.m4b' || this.ext === '.m4a') {
-      return 'audio/mpeg'
-    } else if (this.ext === '.mp4') {
-      return 'audio/mp4'
-    } else if (this.ext === '.ogg') {
-      return 'audio/ogg'
-    } else if (this.ext === '.aac' || this.ext === '.m4p') {
-      return 'audio/aac'
-    }
-    return 'audio/mpeg'
+    return getAudioMimeTypeFromExtname(this.ext) || AudioMimeType.MP3
   }
 
   toJSON() {
diff --git a/server/objects/files/AudioFile.js b/server/objects/files/AudioFile.js
index 35cb61b0..683834ec 100644
--- a/server/objects/files/AudioFile.js
+++ b/server/objects/files/AudioFile.js
@@ -1,4 +1,3 @@
-const { isNullOrNaN } = require('../../utils/index')
 const { AudioMimeType } = require('../../utils/constants')
 const AudioMetaTags = require('../metadata/AudioMetaTags')
 const FileMetadata = require('../metadata/FileMetadata')
diff --git a/server/routers/StaticRouter.js b/server/routers/StaticRouter.js
index 24b6f6da..dcfc8d32 100644
--- a/server/routers/StaticRouter.js
+++ b/server/routers/StaticRouter.js
@@ -1,6 +1,6 @@
 const express = require('express')
 const Path = require('path')
-const Logger = require('../Logger')
+const { getAudioMimeTypeFromExtname } = require('../utils/fileUtils')
 
 class StaticRouter {
   constructor(db) {
@@ -20,7 +20,16 @@ class StaticRouter {
       var fullPath = null
       if (item.isFile) fullPath = item.path
       else fullPath = Path.join(item.path, remainingPath)
-      res.sendFile(fullPath)
+
+      var opts = {}
+
+      // Express does not set the correct mimetype for m4b files so use our defined mimetypes if available
+      const audioMimeType = getAudioMimeTypeFromExtname(Path.extname(fullPath))
+      if (audioMimeType) {
+        opts = { headers: { 'Content-Type': audioMimeType } }
+      }
+
+      res.sendFile(fullPath, opts)
     })
   }
 }
diff --git a/server/utils/fileUtils.js b/server/utils/fileUtils.js
index 0648bd03..f487a209 100644
--- a/server/utils/fileUtils.js
+++ b/server/utils/fileUtils.js
@@ -3,6 +3,7 @@ const rra = require('../libs/recursiveReaddirAsync')
 const axios = require('axios')
 const Path = require('path')
 const Logger = require('../Logger')
+const { AudioMimeType } = require('./constants')
 
 async function getFileStat(path) {
   try {
@@ -211,3 +212,11 @@ module.exports.sanitizeFilename = (filename, colonReplacement = ' - ') => {
 
   return sanitized
 }
+
+// Returns null if extname is not in our defined list of audio extnames
+module.exports.getAudioMimeTypeFromExtname = (extname) => {
+  if (!extname || !extname.length) return null
+  const formatUpper = extname.slice(1).toUpperCase()
+  if (AudioMimeType[formatUpper]) return AudioMimeType[formatUpper]
+  return null
+}
\ No newline at end of file