diff --git a/src/chunk.rs b/src/chunk.rs
index 8e37bc3..7a220b1 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -125,6 +125,7 @@ impl<S: EbmlEventSource> Stream for WebmChunker<S>
                         },
                         Ok(Async::Ready(Some(WebmElement::Info))) => {},
                         Ok(Async::Ready(Some(WebmElement::Void))) => {},
+                        Ok(Async::Ready(Some(WebmElement::Unknown(_)))) => {},
                         Ok(Async::Ready(Some(element))) => {
                             match encode_webm_element(element, buffer) {
                                 Ok(_) => {},
diff --git a/src/webm.rs b/src/webm.rs
index c66bb5d..5386b4a 100644
--- a/src/webm.rs
+++ b/src/webm.rs
@@ -123,7 +123,9 @@ pub fn encode_webm_element<T: Write + Seek>(element: WebmElement, output: &mut T
         WebmElement::Cluster => encode_tag_header(CLUSTER_ID, Varint::Unknown, output),
         WebmElement::Timecode(time) => encode_integer(TIMECODE_ID, time, output),
         WebmElement::SimpleBlock(block) => encode_simple_block(block, output),
-        _ => Err(IoError::new(ErrorKind::InvalidInput, WriteError::OutOfRange))
+        WebmElement::Void => Err(IoError::new(ErrorKind::InvalidInput, WriteError::OutOfRange)),
+        WebmElement::Info => Err(IoError::new(ErrorKind::InvalidInput, WriteError::OutOfRange)),
+        WebmElement::Unknown(_) => Err(IoError::new(ErrorKind::InvalidInput, WriteError::OutOfRange))
     }
 }