diff --git a/apps/casette/encode.py b/apps/casette/encode.py
index 322f81c..690cd60 100644
--- a/apps/casette/encode.py
+++ b/apps/casette/encode.py
@@ -96,7 +96,7 @@ def main() -> None:
     output_path = args.output or args.input.with_name(args.input.stem + ".wav")
 
     tones = FSKWriter(args.sample_rate, args.low_cycles, args.high_cycles, args.low, args.high, args.amplitude)
-    tones.block(0, args.input.name.encode())
+    tones.block(0, args.input.name.encode() + b'\0')
 
 
     tones.finalize()
diff --git a/test.wav b/test.wav
index 5dd4eaa..daadff1 100644
Binary files a/test.wav and b/test.wav differ