diff --git a/datajoint/blob.py b/datajoint/blob.py
index d513532d8..a9a46a327 100644
--- a/datajoint/blob.py
+++ b/datajoint/blob.py
@@ -49,7 +49,7 @@ def pack(obj):
         obj, imaginary = np.real(obj), np.imag(obj)
 
     type_number = reverseClassID[obj.dtype]
-    assert dtypeList[type_number] is obj.dtype, 'ambigous or unknown array type'
+    assert dtypeList[type_number] == obj.dtype, 'ambigous or unknown array type'
     blob += np.asarray(type_number, dtype=np.uint32).tostring()
     blob += np.int8(is_complex).tostring() + b'\0\0\0'
     blob += obj.tostring()
diff --git a/tests/test_relational_operand.py b/tests/test_relational_operand.py
index 9aeca014d..cc54255b5 100644
--- a/tests/test_relational_operand.py
+++ b/tests/test_relational_operand.py
@@ -176,8 +176,8 @@ def test_restrictions_by_lists():
 
     def test_datetime(self):
         """Test date retrieval"""
-        Experiment().populate()
-        e1 = Experiment() & dict(experiment_date='2015-11-20')
-        e2 = Experiment() & dict(experiment_date=datetime.date(2015, 11, 20))
+        date = Experiment().fetch['experiment_date'][0]
 
-        assert_true(len(e1) == len(e2) == 7, 'Two date restriction do not yield the same result')
+        e1 = Experiment() & dict(experiment_date=str(date))
+        e2 = Experiment() & dict(experiment_date=date)
+        assert_true(len(e1) == len(e2) > 0, 'Two date restriction do not yield the same result')