diff --git a/PIL/Jpeg2KImagePlugin.py b/PIL/Jpeg2KImagePlugin.py
index b82acdd98..238500448 100644
--- a/PIL/Jpeg2KImagePlugin.py
+++ b/PIL/Jpeg2KImagePlugin.py
@@ -84,7 +84,8 @@ def _parse_jp2_header(fp):
     size = None
     mode = None
     bpc = None
-
+    nc = None
+    
     hio = io.BytesIO(header)
     while True:
         lbox, tbox = struct.unpack('>I4s', hio.read(8))
@@ -141,6 +142,9 @@ def _parse_jp2_header(fp):
                         mode = 'RGBA'
                     break
 
+    if size is None or mode is None:
+        raise SyntaxError("Malformed jp2 header")
+    
     return (size, mode)
 
 ##
diff --git a/Tests/images/unbound_variable.jp2 b/Tests/images/unbound_variable.jp2
new file mode 100644
index 000000000..ed6d5943e
Binary files /dev/null and b/Tests/images/unbound_variable.jp2 differ
diff --git a/Tests/test_file_jpeg2k.py b/Tests/test_file_jpeg2k.py
index 4b7286a20..7e23e091a 100644
--- a/Tests/test_file_jpeg2k.py
+++ b/Tests/test_file_jpeg2k.py
@@ -170,6 +170,18 @@ class TestFileJpeg2k(PillowTestCase):
         im = self.roundtrip(jp2)
         self.assert_image_equal(im, jp2)
 
+    def test_unbound_local(self):
+        # prepatch, a malformed jp2 file could cause an UnboundLocalError
+        # exception.
+        try:
+            jp2 = Image.open('Tests/images/unbound_variable.jp2')
+            self.assertTrue(False, 'Expecting an exception')
+        except SyntaxError as err:
+            self.assertTrue(True, 'Expecting a syntax error')
+        except IOError as err:
+            self.assertTrue(True, 'Expecting an IO error')
+        except UnboundLocalError as err:
+            self.assertTrue(False, "Prepatch error")
 
 if __name__ == '__main__':
     unittest.main()