diff --git a/skimage/morphology/convex_hull.py b/skimage/morphology/convex_hull.py
index b6e1b43a..d092b122 100644
--- a/skimage/morphology/convex_hull.py
+++ b/skimage/morphology/convex_hull.py
@@ -66,7 +66,7 @@ def convex_hull_image(image):
     return mask
 
 
-def convex_hull_object(image, neighbors=8):
+def convex_hull_object(image, neighbors):
     """Compute the convex hull image of individual objects in a binary image.
 
     The convex hull is the set of pixels included in the smallest convex
diff --git a/skimage/morphology/tests/test_convex_hull.py b/skimage/morphology/tests/test_convex_hull.py
index 8b499709..67d77a31 100644
--- a/skimage/morphology/tests/test_convex_hull.py
+++ b/skimage/morphology/tests/test_convex_hull.py
@@ -69,23 +69,41 @@ def test_possible_hull():
 @skipif(not scipy_spatial)
 def test_object():
     image = np.array(
-        [[1, 0, 1, 0, 0, 0, 0, 0, 0],
-         [1, 0, 1, 0, 1, 0, 0, 0, 1],
-         [0, 1, 0, 0, 0, 1, 0, 0, 1],
-         [0, 0, 0, 0, 0, 0, 1, 0, 1],
-         [0, 0, 0, 0, 0, 0, 0, 1, 0],
+        [[0, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 1, 1, 1, 0, 0, 1, 0, 1],
+         [1, 0, 0, 0, 0, 0, 0, 1, 0],
+         [1, 0, 0, 0, 0, 0, 1, 0, 1],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=bool)
 
-    expected = np.array(
-        [[1, 1, 1, 0, 0, 0, 0, 0, 0],
-         [1, 1, 1, 0, 1, 1, 1, 1, 1],
-         [0, 1, 0, 0, 0, 1, 1, 1, 1],
-         [0, 0, 0, 0, 0, 0, 1, 1, 1],
-         [0, 0, 0, 0, 0, 0, 0, 1, 0],
+    expected4 = np.array(
+        [[0, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 1, 0, 0, 0, 0, 0, 0, 0],
+         [1, 1, 1, 0, 0, 0, 0, 0, 0],
+         [1, 1, 1, 1, 0, 0, 1, 0, 1],
+         [1, 1, 1, 0, 0, 0, 0, 1, 0],
+         [1, 1, 0, 0, 0, 0, 1, 0, 1],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=bool)
 
-    assert_array_equal(convex_hull_object(image), expected)
+    assert_array_equal(convex_hull_object(image, 4), expected4)
 
+    expected8 = np.array(
+        [[0, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [1, 1, 0, 0, 0, 0, 0, 0, 0],
+         [1, 1, 1, 0, 0, 0, 0, 0, 0],
+         [1, 1, 1, 1, 0, 0, 1, 1, 1],
+         [1, 1, 1, 0, 0, 0, 1, 1, 1],
+         [1, 1, 0, 0, 0, 0, 1, 1, 1],
+         [1, 0, 0, 0, 0, 0, 0, 0, 0],
+         [0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=bool)
+
+    assert_array_equal(convex_hull_object(image, 8), expected8)
 
 if __name__ == "__main__":
     np.testing.run_module_suite()