diff --git a/glymur/jp2k.py b/glymur/jp2k.py
index 988e814..6db0198 100644
--- a/glymur/jp2k.py
+++ b/glymur/jp2k.py
@@ -1134,7 +1134,6 @@ def _validate_jp2_box_sequence(boxes):
 
 def _validate_jpx_box_sequence(boxes):
     """Run through series of tests for JPX box legality."""
-    _validate_association(boxes)
     _validate_label(boxes)
     _validate_jpx_brand(boxes, boxes[1].brand)
     _validate_jpx_compatibility(boxes, boxes[1].compatibility_list)
@@ -1283,6 +1282,12 @@ def _validate_top_level(boxes):
     if 'dtbl' in multiples:
         raise IOError('There can only be one dtbl box in a file.')
 
+    # If there is one data reference box, then there must also be one ftbl.
+    if 'dtbl' in count and 'ftbl' not in count:
+        msg = 'The presence of a data reference box requires the presence of '
+        msg += 'a fragment table box as well.'
+        raise IOError(msg)
+
 def _validate_singletons(boxes):
     """Several boxes can only occur once."""
     count = _collect_box_count(boxes)
@@ -1336,23 +1341,6 @@ def _validate_label(boxes):
                 # Same set of checks on any child boxes.
                 _validate_label(box.box)
 
-def _validate_association(boxes):
-    """
-    Association boxes can only contain number list boxes and xml boxes, as far
-    as we know.
-    """
-    for box in boxes:
-        if box.box_id == 'asoc':
-            if box.box[0].box_id != 'nlst' or box.box[1].box_id != 'xml ':
-                msg = "An Association box can only contain a NumberList box "
-                msg += "followed by an XML box."
-                raise RuntimeError(msg)
-        if hasattr(box, 'box') != 0:
-            # Same set of checks on any child boxes.
-            _validate_association(box.box)
-
-
-
 def extract_image_cube(image):
     """Extract 3D image from openjpeg data structure.
     """
diff --git a/glymur/test/test_jp2box_jpx.py b/glymur/test/test_jp2box_jpx.py
index e50d4f9..1eb5198 100644
--- a/glymur/test/test_jp2box_jpx.py
+++ b/glymur/test/test_jp2box_jpx.py
@@ -270,6 +270,7 @@ class TestJPX(unittest.TestCase):
     """Test suite for other JPX boxes."""
 
     def setUp(self):
+        self.jp2file = glymur.data.nemo()
         self.jpxfile = glymur.data.jpxfile()
 
     def tearDown(self):
@@ -354,6 +355,25 @@ class TestJPX(unittest.TestCase):
         self.assertEqual(j.box[16].box[0].box_id, 'free')
         self.assertEqual(type(j.box[16].box[0]), glymur.jp2box.FreeBox)
 
+    def test_data_reference_requires_dtbl(self):
+        """The existance of a data reference box requires a ftbl box as well."""
+        flag = 0
+        version = (0, 0, 0)
+        url1 = 'file:////usr/local/bin'
+        url2 = 'http://glymur.readthedocs.org'
+        jpx1 = glymur.Jp2k(self.jp2file)
+        boxes = jpx1.box
+        boxes[1].brand = 'jpx '
+
+        deurl1 = glymur.jp2box.DataEntryURLBox(flag, version, url1)
+        deurl2 = glymur.jp2box.DataEntryURLBox(flag, version, url2)
+        dref = glymur.jp2box.DataReferenceBox([deurl1, deurl2])
+        boxes.append(dref)
+
+        with tempfile.NamedTemporaryFile(suffix='.jpx') as tfile:
+            with self.assertRaises(IOError):
+                jpx2 = jpx1.wrap(tfile.name, boxes=boxes)
+
     def test_dtbl(self):
         """Verify that we can interpret Data Reference boxes."""
         # Copy the existing JPX file, add a data reference box onto the end.