diff --git a/src/PIL/JpegXlImagePlugin.py b/src/PIL/JpegXlImagePlugin.py
index 324c453ea..7326ace46 100644
--- a/src/PIL/JpegXlImagePlugin.py
+++ b/src/PIL/JpegXlImagePlugin.py
@@ -50,13 +50,13 @@ class JpegXlImageFile(ImageFile.ImageFile):
         self.is_animated = has_anim
 
         self._tps_dur_secs = 1
-        self.n_frames = 1
+        self.n_frames: Optional[int] = 1
         if self.is_animated:
             self.n_frames = None
             if n_frames > 0:
                 self.n_frames = n_frames
                 self._tps_dur_secs = tps_num / tps_denom
-
+        
         # TODO: handle libjxl time codes
         self.__timestamp = 0
 
@@ -73,7 +73,7 @@ class JpegXlImageFile(ImageFile.ImageFile):
 
         self._rewind()
 
-    def _fix_exif(self, exif: bytes) -> bytes:
+    def _fix_exif(self, exif: bytes) -> Optional[bytes]:
         # jpeg xl does some weird shenanigans when storing exif
         # it omits first 6 bytes of tiff header but adds 4 byte offset instead
         if len(exif) <= 4:
@@ -81,7 +81,7 @@ class JpegXlImageFile(ImageFile.ImageFile):
         exif_start_offset = struct.unpack(">I", exif[:4])[0]
         return exif[exif_start_offset + 4 :]
 
-    def _getexif(self) -> dict[str, str]:
+    def _getexif(self) -> Optional[dict[str, str]]:
         if "exif" not in self.info:
             return None
         return self.getexif()._get_merged_dict()
@@ -112,7 +112,7 @@ class JpegXlImageFile(ImageFile.ImageFile):
 
         return data, timestamp, duration, is_last
 
-    def _rewind(self, hard: bool = False) -> None:
+    def _rewind(self, hard: bool=False) -> None:
         if hard:
             self._decoder.rewind()
         self.__physical_frame = 0