diff --git a/examples/hlb_cifar10.py b/examples/hlb_cifar10.py
index f6194aaed9..759d042ec9 100644
--- a/examples/hlb_cifar10.py
+++ b/examples/hlb_cifar10.py
@@ -49,7 +49,7 @@ class UnsyncedBatchNorm:
       # https://github.com/pytorch/pytorch/blob/c618dc13d2aa23625cb0d7ada694137532a4fa33/aten/src/ATen/native/cuda/Normalization.cuh
       # There's "online" algorithms that fix this, like https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
       batch_mean = x.mean(axis=(1,3,4))
-      y = (x - batch_mean.reshape(shape=[batch_mean.shape[0], 1, -1, 1, 1]))
+      y = (x - batch_mean.detach().reshape(shape=[batch_mean.shape[0], 1, -1, 1, 1]))  # d(var)/d(mean) = 0
       batch_var = (y*y).mean(axis=(1,3,4))
       batch_invstd = batch_var.add(self.eps).pow(-0.5)
 
diff --git a/test/test_schedule.py b/test/test_schedule.py
index 58570a7017..98cc2ca5a9 100644
--- a/test/test_schedule.py
+++ b/test/test_schedule.py
@@ -208,7 +208,7 @@ class TestSchedule(unittest.TestCase):
       opt.zero_grad()
       img_bn.backward()
       # this is too high
-      check_schedule(opt.schedule_step(), 18)
+      check_schedule(opt.schedule_step(), 17)
 
   def test_fold_conv_relu(self):
     c1 = nn.Conv2d(3,16,3)
diff --git a/tinygrad/nn/__init__.py b/tinygrad/nn/__init__.py
index a02f4b31b4..c04c1644f1 100644
--- a/tinygrad/nn/__init__.py
+++ b/tinygrad/nn/__init__.py
@@ -20,7 +20,7 @@ class BatchNorm2d:
       # https://github.com/pytorch/pytorch/blob/c618dc13d2aa23625cb0d7ada694137532a4fa33/aten/src/ATen/native/cuda/Normalization.cuh
       # There's "online" algorithms that fix this, like https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
       batch_mean = x.mean(axis=(0,2,3))
-      y = (x - batch_mean.reshape(shape=[1, -1, 1, 1]))
+      y = (x - batch_mean.detach().reshape(shape=[1, -1, 1, 1]))  # d(var)/d(mean) = 0
       batch_var = (y*y).mean(axis=(0,2,3))
       batch_invstd = batch_var.add(self.eps).pow(-0.5)