diff --git a/tests/pipeline/test_adjustment.py b/tests/pipeline/test_adjustment.py
index 69f8294a..9e31041e 100644
--- a/tests/pipeline/test_adjustment.py
+++ b/tests/pipeline/test_adjustment.py
@@ -35,6 +35,21 @@ class AdjustmentTestCase(TestCase):
         )
         self.assertEqual(result, expected)
 
+    def test_make_int_adjustment(self):
+        result = adj.make_adjustment_from_indices(
+            1, 2, 3, 4,
+            adjustment_kind=adj.OVERWRITE,
+            value=1,
+        )
+        expected = adj.Int64Overwrite(
+            first_row=1,
+            last_row=2,
+            first_col=3,
+            last_col=4,
+            value=1,
+        )
+        self.assertEqual(result, expected)
+
     def test_make_datetime_adjustment(self):
         overwrite_dt = make_datetime64ns(0)
         result = adj.make_adjustment_from_indices(
@@ -51,15 +66,12 @@ class AdjustmentTestCase(TestCase):
         )
         self.assertEqual(result, expected)
 
-    def test_make_object_adjustment(self):
-        class SomeClass(object):
-            pass
-        my_value = SomeClass()
-
+    @parameterized.expand([("some text",), ("some text".encode(),), (None,)])
+    def test_make_object_adjustment(self, value):
         result = adj.make_adjustment_from_indices(
             1, 2, 3, 4,
             adjustment_kind=adj.OVERWRITE,
-            value=my_value,
+            value=value,
         )
 
         expected = adj.ObjectOverwrite(
@@ -67,6 +79,24 @@ class AdjustmentTestCase(TestCase):
             last_row=2,
             first_col=3,
             last_col=4,
-            value=my_value,
+            value=value,
         )
         self.assertEqual(result, expected)
+
+    def test_unsupported_type(self):
+        class SomeClass(object):
+            pass
+
+        with self.assertRaises(TypeError) as e:
+            adj.make_adjustment_from_indices(
+                1, 2, 3, 4,
+                adjustment_kind=adj.OVERWRITE,
+                value=SomeClass(),
+            )
+
+        exc = e.exception
+        expected_msg = (
+            "Don't know how to make overwrite adjustments for values of type "
+            "%r." % SomeClass
+        )
+        self.assertEqual(str(exc), expected_msg)