diff --git a/activestorage/storage.py b/activestorage/storage.py
index 65c648e..80a575b 100644
--- a/activestorage/storage.py
+++ b/activestorage/storage.py
@@ -49,7 +49,7 @@ def reduce_chunk(rfile,
         if tmp.size:
             return method(tmp), tmp.size
         else:
-            return tmp, None
+            return tmp, 0
     else:
         return tmp, None
 
diff --git a/tests/unit/test_storage.py b/tests/unit/test_storage.py
index 1f04121..8e27972 100644
--- a/tests/unit/test_storage.py
+++ b/tests/unit/test_storage.py
@@ -60,7 +60,7 @@ def test_reduced_chunk_fully_masked_data_fill():
                          order="C", chunk_selection=ch_sel,
                          method=np.mean)
     assert rc[0].size == 0
-    assert rc[1] is None
+    assert rc[1] == 0
 
 
 def test_reduced_chunk_fully_masked_data_missing():
@@ -79,7 +79,7 @@ def test_reduced_chunk_fully_masked_data_missing():
                          order="C", chunk_selection=ch_sel,
                          method=np.mean)
     assert rc[0].size == 0
-    assert rc[1] is None
+    assert rc[1] == 0
 
 
 def test_reduced_chunk_fully_masked_data_vmin():
@@ -98,7 +98,7 @@ def test_reduced_chunk_fully_masked_data_vmin():
                          order="C", chunk_selection=ch_sel,
                          method=np.mean)
     assert rc[0].size == 0
-    assert rc[1] is None
+    assert rc[1] == 0
 
 
 def test_reduced_chunk_fully_masked_data_vmax():
@@ -117,7 +117,7 @@ def test_reduced_chunk_fully_masked_data_vmax():
                          order="C", chunk_selection=ch_sel,
                          method=np.mean)
     assert rc[0].size == 0
-    assert rc[1] is None
+    assert rc[1] == 0
 
 
 def test_zero_data():