diff --git a/Tests/test_image.py b/Tests/test_image.py
index 0e085d6e4..214f2668f 100644
--- a/Tests/test_image.py
+++ b/Tests/test_image.py
@@ -582,6 +582,10 @@ class TestImage:
         assert ext_individual == ext_multiple
 
     def test_remap_palette(self):
+        # Test identity transform
+        with Image.open("Tests/images/hopper.gif") as im:
+            assert_image_equal(im, im.remap_palette(list(range(256))))
+
         # Test illegal image mode
         with hopper() as im:
             with pytest.raises(ValueError):
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 76814a8cc..f06d3bdbc 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1796,6 +1796,7 @@ class Image:
 
         if source_palette is None:
             if self.mode == "P":
+                self.load()
                 real_source_palette = self.im.getpalette("RGB")[:768]
             else:  # L-mode
                 real_source_palette = bytearray(i // 3 for i in range(768))