diff --git a/src/PIL/ImageFile.py b/src/PIL/ImageFile.py
index 339917ab7..63a9d4ca2 100644
--- a/src/PIL/ImageFile.py
+++ b/src/PIL/ImageFile.py
@@ -174,8 +174,8 @@ class ImageFile(Image.Image):
                     else:
                         # use mmap, if possible
                         import mmap
-                        fp = open(self.filename, "r")
-                        self.map = mmap.mmap(fp.fileno(), 0, access=mmap.ACCESS_READ)
+                        with open(self.filename, "r") as fp:
+                            self.map = mmap.mmap(fp.fileno(), 0, access=mmap.ACCESS_READ)
                         self.im = Image.core.map_buffer(
                             self.map, self.size, decoder_name, extents, offset, args
                             )