diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 09080e7b2..92b9a8c7e 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -313,6 +313,12 @@ namespace MediaBrowser.Controller.MediaEncoding
                 return null;
             }
 
+            // ISO files don't have an ffmpeg format
+            if (string.Equals(container, "iso", StringComparison.OrdinalIgnoreCase))
+            {
+                return null;
+            }
+
             return container;
         }
 
diff --git a/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs b/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
index 47cf020b4..205933ae2 100644
--- a/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
+++ b/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
@@ -370,7 +370,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
         public string GetInputArgument(string inputFile, MediaSourceInfo mediaSource)
         {
             var prefix = "file";
-            if (mediaSource.VideoType == VideoType.BluRay || mediaSource.VideoType == VideoType.Iso)
+            if (mediaSource.VideoType == VideoType.BluRay)
             {
                 prefix = "bluray";
             }