BUG: Fix __getitem__ on masked arrays containing np.ma.masked

2 files changed, 19 insertions, 1 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index 50a58f86b..8179dc930 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -3244,7 +3244,9 @@ class MaskedArray(ndarray):
                 return mvoid(dout, mask=mout, hardmask=self._hardmask)
 
             # special case introduced in gh-5962
-            elif self.dtype.type is np.object_ and isinstance(dout, np.ndarray):
+            elif (self.dtype.type is np.object_ and
+                  isinstance(dout, np.ndarray) and
+                  dout is not masked):
                 # If masked, turn into a MaskedArray, with everything masked.
                 if mout:
                     return MaskedArray(dout, mask=True)
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
index 1bd59d593..35c55894d 100644
--- a/numpy/ma/tests/test_core.py
+++ b/numpy/ma/tests/test_core.py
@@ -4471,6 +4471,22 @@ class TestMaskedObjectArray(TestCase):
             assert_equal(arr[0,...][()].data, a0)
             assert_equal(arr[0,...][()].mask, True)
 
+    def test_nested_ma(self):
+
+        arr = np.ma.array([None, None])
+        # set the first object to be an unmasked masked constant. A little fiddly
+        arr[0,...] = np.array([np.ma.masked], object)[0,...]
+
+        # check the above line did what we were aiming for
+        assert_(arr.data[0] is np.ma.masked)
+
+        # test that getitem returned the value by identity
+        assert_(arr[0] is np.ma.masked)
+
+        # now mask the masked value!
+        arr[0] = np.ma.masked
+        assert_(arr[0] is np.ma.masked)
+
 
 class TestMaskedView(TestCase):