diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 55861a75af0..b8b840651a6 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1634,7 +1634,7 @@ def putalpha(self, alpha):
                     self.im = im
                 self.pyaccess = None
                 self.mode = self.im.mode
-            except (KeyError, ValueError) as e:
+            except KeyError as e:
                 raise ValueError("illegal image mode") from e
 
         if self.mode in ("LA", "PA"):