--- a/buggy.py
+++ b/buggy.py
@@ -6,7 +6,7 @@
 def build_message(header: str, raw_chunks: list[bytes]) -> str:
     """Build a text message: header followed by decoded payload."""
     payload = read_chunks(raw_chunks)
-    return header + ": " + payload
+    return header + ": " + payload.decode("utf-8")
 
 
 def parse_pipeline(header: str, raw_chunks: list[bytes]) -> dict[str, str]:
