diff --git a/glymur/jp2box.py b/glymur/jp2box.py
index d4a44e9..aa92f2a 100644
--- a/glymur/jp2box.py
+++ b/glymur/jp2box.py
@@ -59,6 +59,11 @@ class Jp2kBox(object):
         msg += " @ ({0}, {1})".format(self.offset, self.length)
         return msg
 
+    def _write(self, f):
+        """Must be implemented in a subclass.
+        """
+        raise NotImplementedError("Not supported for this box.")
+
     def _parse_superbox(self, f):
         """Parse a superbox (box consisting of nothing but other boxes.
 
@@ -882,8 +887,10 @@ class JPEG2000SignatureBox(Jp2kBox):
         Four-byte tuple identifying the file as JPEG 2000.
     """
     def __init__(self, **kwargs):
-        Jp2kBox.__init__(self, id='', longname='JPEG 2000 Signature')
+        Jp2kBox.__init__(self, id='jP  ', longname='JPEG 2000 Signature')
         self.__dict__.update(**kwargs)
+        if 'signature' not in kwargs.keys():
+            self.signature = (13, 10, 135, 10)
 
     def __str__(self):
         msg = Jp2kBox.__str__(self)
diff --git a/glymur/test/test_jp2box.py b/glymur/test/test_jp2box.py
new file mode 100644
index 0000000..40b85b8
--- /dev/null
+++ b/glymur/test/test_jp2box.py
@@ -0,0 +1,27 @@
+import unittest
+
+import numpy as np
+import pkg_resources
+
+import glymur
+
+@unittest.skipIf(glymur.lib.openjp2._OPENJP2 is None,
+                 "Missing openjp2 library.")
+class TestJp2Boxes(unittest.TestCase):
+
+    def setUp(self):
+        self.jp2file = pkg_resources.resource_filename(glymur.__name__,
+                                                       "data/nemo.jp2")
+
+    def tearDown(self):
+        pass
+
+    def test_default_JPEG2000SignatureBox(self):
+        # Should be able to instantiate a JPEG2000SignatureBox 
+        b = glymur.jp2box.JPEG2000SignatureBox()
+        self.assertEqual(b.signature, (13, 10, 135, 10))
+
+
+if __name__ == "__main__":
+    unittest.main()
+