diff --git a/kitty/clipboard.py b/kitty/clipboard.py
index 854c4f702..0623f50e6 100644
--- a/kitty/clipboard.py
+++ b/kitty/clipboard.py
@@ -72,6 +72,8 @@ class Clipboard:
 
     def __call__(self, mime: str) -> Callable[[], bytes]:
         data = self.data.get(mime, b'')
+        if isinstance(data, str):  # type: ignore
+            data = data.encode('utf-8')  # type: ignore
         if isinstance(data, bytes):
             def chunker() -> bytes:
                 nonlocal data