diff --git a/rembg/commands/b_command.py b/rembg/commands/b_command.py
index 702458e6..21fc64a1 100644
--- a/rembg/commands/b_command.py
+++ b/rembg/commands/b_command.py
@@ -135,7 +135,9 @@ def b_command(
             os.makedirs(output_dir, exist_ok=True)
 
     def img_to_byte_array(img: PILImage) -> bytes:
-        return img.convert('RGB').tobytes("raw", "RGB")
+        buff = io.BytesIO()
+        img.save(buff, format="PNG")
+        return buff.getvalue()
 
     async def connect_stdin_stdout():
         loop = asyncio.get_event_loop()