diff --git a/src/source/mix.rs b/src/source/mix.rs
index c9df4c03..3c011b88 100644
--- a/src/source/mix.rs
+++ b/src/source/mix.rs
@@ -123,6 +123,7 @@ where
 
     #[inline]
     fn try_seek(&mut self, pos: Duration) -> Result<(), SeekNotSupported> {
+        todo!("should check if both inputs support seeking");
         self.input1.try_seek(pos)?;
         self.input2.try_seek(pos)
     }