diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 76ea48510..6dee3fe23 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1128,7 +1128,10 @@ class Image:
                 del new_im.info["transparency"]
             if trns is not None:
                 try:
-                    new_im.info["transparency"] = new_im.palette.getcolor(trns, new_im)
+                    new_im.info["transparency"] = new_im.palette.getcolor(
+                        cast(Tuple[int, int, int], trns),  # trns was converted to RGB
+                        new_im,
+                    )
                 except Exception:
                     # if we can't make a transparent color, don't leave the old
                     # transparency hanging around to mess us up.
@@ -1178,7 +1181,10 @@ class Image:
         if trns is not None:
             if new_im.mode == "P":
                 try:
-                    new_im.info["transparency"] = new_im.palette.getcolor(trns, new_im)
+                    new_im.info["transparency"] = new_im.palette.getcolor(
+                        cast(Tuple[int, int, int], trns),  # trns was converted to RGB
+                        new_im,
+                    )
                 except ValueError as e:
                     del new_im.info["transparency"]
                     if str(e) != "cannot allocate more than 256 colors":