diff --git a/MediaBrowser.Api/Playback/BaseStreamingService.cs b/MediaBrowser.Api/Playback/BaseStreamingService.cs
index eb44cb4266..b92ea6d1f4 100644
--- a/MediaBrowser.Api/Playback/BaseStreamingService.cs
+++ b/MediaBrowser.Api/Playback/BaseStreamingService.cs
@@ -131,6 +131,8 @@ namespace MediaBrowser.Api.Playback
         /// </summary>
         private string GetOutputFilePath(StreamState state, EncodingOptions encodingOptions, string outputFileExtension)
         {
+            if (outputFileExtension == null) outputFileExtension = "";
+            
             var data = $"{state.MediaPath}-{state.UserAgent}-{state.Request.DeviceId}-{state.Request.PlaySessionId}";
 
             var filename = data.GetMD5().ToString("N", CultureInfo.InvariantCulture);