diff --git a/ext/bg/js/audio-downloader.js b/ext/bg/js/audio-downloader.js
index 62abda8f..25c25250 100644
--- a/ext/bg/js/audio-downloader.js
+++ b/ext/bg/js/audio-downloader.js
@@ -252,7 +252,9 @@ class AudioDownloader {
             throw new Error('Could not retrieve audio');
         }
 
-        return this._arrayBufferToBase64(arrayBuffer);
+        const data = this._arrayBufferToBase64(arrayBuffer);
+        const contentType = response.headers.get('Content-Type');
+        return {data, contentType};
     }
 
     async _isAudioBinaryValid(arrayBuffer, source) {
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 465c8137..e5f8466e 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -1604,8 +1604,9 @@ class Backend {
 
         const {sources, customSourceUrl, customSourceType} = details;
         let data;
+        let contentType;
         try {
-            data = await this._downloadDefinitionAudio(
+            ({data, contentType} = await this._downloadDefinitionAudio(
                 sources,
                 expression,
                 reading,
@@ -1616,13 +1617,15 @@ class Backend {
                     binary: true,
                     disableCache: true
                 }
-            );
+            ));
         } catch (e) {
             // No audio
             return null;
         }
 
-        let fileName = this._generateAnkiNoteMediaFileName('yomichan_audio', '.mp3', timestamp, definitionDetails);
+        let extension = this._mediaUtility.getFileExtensionFromAudioMediaType(contentType);
+        if (extension === null) { extension = '.mp3'; }
+        let fileName = this._generateAnkiNoteMediaFileName('yomichan_audio', extension, timestamp, definitionDetails);
         fileName = fileName.replace(/\]/g, '');
         await ankiConnect.storeMediaFile(fileName, data);
 
diff --git a/ext/bg/js/media-utility.js b/ext/bg/js/media-utility.js
index b50b2481..b4fbe04d 100644
--- a/ext/bg/js/media-utility.js
+++ b/ext/bg/js/media-utility.js
@@ -98,4 +98,35 @@ class MediaUtility {
                 return null;
         }
     }
+
+    /**
+     * Gets the file extension for a corresponding media type.
+     * @param mediaType The media type to use.
+     * @returns A file extension including the dot for the media type,
+     *   otherwise null.
+     */
+    getFileExtensionFromAudioMediaType(mediaType) {
+        switch (mediaType) {
+            case 'audio/mpeg':
+            case 'audio/mp3':
+                return '.mp3';
+            case 'audio/mp4':
+                return '.mp4';
+            case 'audio/ogg':
+            case 'audio/vorbis':
+                return '.ogg';
+            case 'audio/vnd.wav':
+            case 'audio/wave':
+            case 'audio/wav':
+            case 'audio/x-wav':
+            case 'audio/x-pn-wav':
+                return '.wav';
+            case 'audio/flac':
+                return '.flac';
+            case 'audio/webm':
+                return '.webm';
+            default:
+                return null;
+        }
+    }
 }