diff --git a/PIL/ImageFile.py b/PIL/ImageFile.py
index 82691af92..79faff797 100644
--- a/PIL/ImageFile.py
+++ b/PIL/ImageFile.py
@@ -196,6 +196,9 @@ class ImageFile(Image.Image):
             except AttributeError:
                 prefix = b""
 
+            # Buffer length read; assign a default value
+            t = 0
+
             for d, e, o, a in self.tile:
                 d = Image._getdecoder(self.mode, d, a, self.decoderconfig)
                 seek(o)