diff --git a/CHANGES.rst b/CHANGES.rst
index db294356..dafb2dac 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -10,8 +10,13 @@ API Changes
 ^^^^^^^^^^^
 
 - ``BoxcarExtract`` and ``HorneExtract`` now accept parameters (and require the image and trace)
-  at initialization, and allow overriding any input parameters when calling. [#117]
+  at initialization, and allow overriding any input parameters when calling [#117]
 
+Bug Fixes
+^^^^^^^^^
+
+- Corrected the default mask created in ``HorneExtract``/``OptimalExtract``
+  when a user doesn't specify one and gives their image as a numpy array [#118]
 
 1.0.0
 -----
diff --git a/specreduce/extract.py b/specreduce/extract.py
index 3a22a5e4..62d28bd5 100644
--- a/specreduce/extract.py
+++ b/specreduce/extract.py
@@ -333,7 +333,7 @@ def __call__(self, image=None, trace_object=None,
 
             # check optional arguments, filling them in if absent
             if mask is None:
-                mask = np.ma.masked_invalid(image)
+                mask = np.ma.masked_invalid(image).mask
             elif image.shape != mask.shape:
                 raise ValueError('image and mask shapes must match.')
 
diff --git a/specreduce/tests/test_extract.py b/specreduce/tests/test_extract.py
index 323e27dd..69a626c5 100644
--- a/specreduce/tests/test_extract.py
+++ b/specreduce/tests/test_extract.py
@@ -4,7 +4,7 @@
 import astropy.units as u
 from astropy.nddata import CCDData
 
-from specreduce.extract import BoxcarExtract, HorneExtract
+from specreduce.extract import BoxcarExtract, HorneExtract, OptimalExtract
 from specreduce.tracing import FlatTrace, ArrayTrace
 
 
@@ -79,6 +79,36 @@ def test_boxcar_array_trace():
     assert np.allclose(spectrum.flux.value, np.full_like(spectrum.flux.value, 75.))
 
 
+def test_horne_array_validation():
+    #
+    # Test HorneExtract scenarios specific to its use with an image of
+    # type `~numpy.ndarray` (instead of the default `~astropy.nddata.NDData`).
+    #
+    trace = FlatTrace(image, 15.0)
+    extract = OptimalExtract(image.data, trace)  # equivalent to HorneExtract
+
+    # an array-type image must come with a variance argument
+    with pytest.raises(ValueError, match=r'.*array.*variance.*specified.*'):
+        ext = extract()
+
+    # an array-type image must have the same dimensions as its variance argument
+    with pytest.raises(ValueError, match=r'.*shapes must match.*'):
+        err = np.ones_like(image[0])
+        ext = extract(variance=err)
+
+    # an array-type image must have the same dimensions as its mask argument
+    with pytest.raises(ValueError, match=r'.*shapes must match.*'):
+        err = np.ones_like(image)
+        mask = np.zeros_like(image[0])
+        ext = extract(variance=err, mask=mask)
+
+    # an array-type image given without mask and unit arguments is fine
+    # and produces a unitless result
+    err = np.ones_like(image)
+    ext = extract(variance=err)
+    assert ext.unit == u.Unit()
+
+
 def test_horne_variance_errors():
     trace = FlatTrace(image, 3.0)