diff --git a/mlem/contrib/docker/context.py b/mlem/contrib/docker/context.py
index 0058ad30..185bf98c 100644
--- a/mlem/contrib/docker/context.py
+++ b/mlem/contrib/docker/context.py
@@ -398,6 +398,8 @@ def write_local_sources(self, requirements: Requirements):
             logger.debug('Putting model source "%s" to distribution...', path)
             full_path = posixpath.join(self.path, path)
             self.fs.makedirs(posixpath.dirname(full_path), exist_ok=True)
+            if isinstance(src, str):  # type: ignore
+                src = src.encode()  # type: ignore
             with self.fs.open(full_path, "wb") as f:
                 f.write(src)