diff --git a/schema/serde/meridian_serde.py b/schema/serde/meridian_serde.py
index ab080cb35..6532f6bed 100644
--- a/schema/serde/meridian_serde.py
+++ b/schema/serde/meridian_serde.py
@@ -362,7 +362,7 @@ def save_meridian(
     if file_path.endswith('.binpb'):
       f.write(serialized_kernel.SerializeToString())
     elif file_path.endswith('.textproto') or file_path.endswith('.txtpb'):
-      f.write(text_format.MessageToString(serialized_kernel))
+      f.write(text_format.MessageToString(serialized_kernel).encode('utf-8'))
     else:
       raise ValueError(f'Unsupported file type: {file_path}')