diff --git a/PIL/MspImagePlugin.py b/PIL/MspImagePlugin.py
index b60a21d69..11d31880c 100644
--- a/PIL/MspImagePlugin.py
+++ b/PIL/MspImagePlugin.py
@@ -15,7 +15,11 @@
 #
 # See the README file for information on usage and redistribution.
 #
-
+# More info on this format: https://archive.org/details/gg243631
+# Page 313:
+# Figure 205. Windows Paint Version 1: "DanM" Format
+# Figure 206. Windows Paint Version 2: "LinS" Format. Used in Windows V2.03
+#
 
 from . import Image, ImageFile
 from ._binary import i16le as i16, o16le as o16
@@ -92,6 +96,7 @@ def _save(im, fp, filename):
     # image body
     ImageFile._save(im, fp, [("raw", (0, 0)+im.size, 32, ("1", 0, 1))])
 
+
 #
 # registry
 
diff --git a/Tests/test_file_msp.py b/Tests/test_file_msp.py
index e174d0061..44fc0ec3b 100644
--- a/Tests/test_file_msp.py
+++ b/Tests/test_file_msp.py
@@ -24,6 +24,15 @@ class TestFileMsp(PillowTestCase):
         self.assertRaises(SyntaxError,
                           lambda: MspImagePlugin.MspImageFile(invalid_file))
 
+    def test_bad_checksum(self):
+        # Arrange
+        # This was created by forcing Pillow to save with checksum=0
+        bad_checksum = "Tests/images/hopper_bad_checksum.msp"
+
+        # Act / Assert
+        self.assertRaises(SyntaxError,
+                          lambda: MspImagePlugin.MspImageFile(bad_checksum))
+
     def test_open(self):
         # Arrange
         # Act