diff --git a/test/test_dtype.py b/test/test_dtype.py
index e28a1972..3027e6a7 100644
--- a/test/test_dtype.py
+++ b/test/test_dtype.py
@@ -638,10 +638,11 @@ class TestAutoCastType(unittest.TestCase):
 
   @unittest.skipUnless(is_dtype_supported(dtypes.half), "need half")
   def test_mean_half_precision_overflow(self):
-    t = Tensor([60000, 60000, 60000], dtype=dtypes.half, requires_grad=True)
+    N = 256
+    t = Tensor([60000] * N*N, dtype=dtypes.half, requires_grad=True).reshape(N, N)
     np.testing.assert_allclose(t.mean().numpy(), 60000)
     t.square().mean().backward()
-    np.testing.assert_allclose(t.grad.numpy(), [60000 * 2 / 3] * 3)
+    np.testing.assert_allclose(t.grad.numpy().flatten(), [60000 * 2 / (N*N)] * N*N)
 
 class TestImplicitFunctionTypeChange(unittest.TestCase):
   def test_functions(self):