diff --git a/altair/utils/save.py b/altair/utils/save.py
index af2c7a981..1784cc43e 100644
--- a/altair/utils/save.py
+++ b/altair/utils/save.py
@@ -142,7 +142,9 @@ def perform_save():
 
         if format == "json":
             json_spec = json.dumps(spec, **json_kwds)
-            write_file_or_filename(fp, json_spec, mode="w")
+            write_file_or_filename(
+                fp, json_spec, mode="w", encoding=kwargs.get("encoding", "utf-8")
+            )
         elif format == "html":
             if inline:
                 kwargs["template"] = "inline"
@@ -157,7 +159,12 @@ def perform_save():
                 json_kwds=json_kwds,
                 **kwargs,
             )
-            write_file_or_filename(fp, mimebundle["text/html"], mode="w")
+            write_file_or_filename(
+                fp,
+                mimebundle["text/html"],
+                mode="w",
+                encoding=kwargs.get("encoding", "utf-8"),
+            )
         elif format in ["png", "svg", "pdf", "vega"]:
             mimebundle = spec_to_mimebundle(
                 spec=spec,
diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 730c2e107..c87c2e85d 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -3247,7 +3247,7 @@ def add_selection(self, *selections) -> Self:
 
 
 def repeat(
-    repeater: Literal["row", "column", "repeat", "layer"] = "repeat"
+    repeater: Literal["row", "column", "repeat", "layer"] = "repeat",
 ) -> core.RepeatRef:
     """Tie a channel to the row or column within a repeated chart