diff --git a/Tests/images/no_palette_after_rgb.gif b/Tests/images/no_palette_after_rgb.gif
new file mode 100644
index 000000000..8704c464c
Binary files /dev/null and b/Tests/images/no_palette_after_rgb.gif differ
diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index 68cb8a36e..887b6b018 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -83,6 +83,15 @@ def test_l_mode_transparency():
         assert im.load()[0, 0] == 128
 
 
+def test_l_mode_after_rgb():
+    with Image.open("Tests/images/no_palette_after_rgb.gif") as im:
+        im.seek(1)
+        assert im.mode == "RGB"
+
+        im.seek(2)
+        assert im.mode == "RGB"
+
+
 def test_strategy():
     with Image.open("Tests/images/chi.gif") as im:
         expected_zero = im.convert("RGB")
diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
index 2e11df54c..1b40b9ad7 100644
--- a/src/PIL/GifImagePlugin.py
+++ b/src/PIL/GifImagePlugin.py
@@ -432,16 +432,13 @@ class GifImageFile(ImageFile.ImageFile):
                 self.mode = "RGB"
                 self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
             return
-        if self.mode == "P" and self._prev_im:
-            if self._frame_transparency is not None:
-                self.im.putpalettealpha(self._frame_transparency, 0)
-                frame_im = self.im.convert("RGBA")
-            else:
-                frame_im = self.im.convert("RGB")
+        if not self._prev_im:
+            return
+        if self._frame_transparency is not None:
+            self.im.putpalettealpha(self._frame_transparency, 0)
+            frame_im = self.im.convert("RGBA")
         else:
-            if not self._prev_im:
-                return
-            frame_im = self.im
+            frame_im = self.im.convert("RGB")
         frame_im = self._crop(frame_im, self.dispose_extent)
 
         self.im = self._prev_im