diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index e54d67a0d508..690828cc86a0 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -7086,21 +7086,14 @@ def test_1d_no_format(self):
     def test_1d_format(self):
         # until gh-5543, ensure that the behaviour matches what it used to be
         a = np.array([np.pi])
-
-        def ret_and_exc(f, *args, **kwargs):
-            try:
-                return f(*args, **kwargs), None
-            except Exception as e:
-                # exceptions don't compare equal, so return type and args
-                # which do
-                return None, (type(e), e.args)
-
-        # Could switch on python version here, but all we care about is
-        # that the behaviour hasn't changed
-        assert_equal(
-            ret_and_exc(object.__format__, a, '30'),
-            ret_and_exc('{:30}'.format, a)
-        )
+        if sys.version_info[:2] >= (3, 4):
+            assert_raises(TypeError, '{:30}'.format, a)
+        else:
+            with suppress_warnings() as sup:
+                sup.filter(PendingDeprecationWarning)
+                res = '{:30}'.format(a)
+                dst = object.__format__(a, '30')
+                assert_equal(res, dst)
 
 
 class TestCTypes(object):
diff --git a/numpy/testing/nose_tools/utils.py b/numpy/testing/nose_tools/utils.py
index 973e3bb4bcad..6c77e5e21e26 100644
--- a/numpy/testing/nose_tools/utils.py
+++ b/numpy/testing/nose_tools/utils.py
@@ -394,14 +394,17 @@ def assert_equal(actual, desired, err_msg='', verbose=True):
         isdesnat = isnat(desired)
         isactnat = isnat(actual)
         dtypes_match = array(desired).dtype.type == array(actual).dtype.type
-        if isdesnat and isactnat and dtypes_match:
+        if isdesnat and isactnat:
             # If both are NaT (and have the same dtype -- datetime or
             # timedelta) they are considered equal.
-            return
+            if dtypes_match:
+                return
+            else:
+                raise AssertionError(msg)
+
     except (TypeError, ValueError, NotImplementedError):
         pass
 
-
     try:
         # Explicitly use __eq__ for comparison, gh-2552
         if not (desired == actual):