diff --git a/ioos_qc/qartod.py b/ioos_qc/qartod.py
index c256dfc..0eaf2e5 100644
--- a/ioos_qc/qartod.py
+++ b/ioos_qc/qartod.py
@@ -372,8 +372,9 @@ def check(self, tinp, inp, zinp):
                 with np.errstate(invalid='ignore'):
                     z_idx = (~zinp.mask) & (zinp >= m.zspan.minv) & (zinp <= m.zspan.maxv)
             else:
-                # Only test the values with masked Z, ie values with no Z
-                z_idx = zinp.mask
+                # If there is no z data in the config, don't try to filter by depth!
+                # Set z_idx to all True to prevent filtering
+                z_idx = np.ones(inp.size, dtype=bool)
 
             # Combine the T and Z indexes
             values_idx = (t_idx & z_idx)
diff --git a/tests/test_qartod.py b/tests/test_qartod.py
index 51c2bcc..26e2e4e 100644
--- a/tests/test_qartod.py
+++ b/tests/test_qartod.py
@@ -857,7 +857,7 @@ def test_climatology_test_depths(self):
                 101
             )
         ]
-        expected_result = [1, 1, 1, 3, 3, 2]
+        expected_result = [1, 1, 1, 3, 3, 3]
         self._run_test(test_inputs, expected_result)