diff --git a/deepmd/pt/model/atomic_model/linear_atomic_model.py b/deepmd/pt/model/atomic_model/linear_atomic_model.py
index 68705049ae..66d19c0a02 100644
--- a/deepmd/pt/model/atomic_model/linear_atomic_model.py
+++ b/deepmd/pt/model/atomic_model/linear_atomic_model.py
@@ -486,7 +486,7 @@ def _compute_weight(
             dim=-1,
         )  # handle masked nnei.
 
-        sigma = numerator / denominator  # nfrmes, nloc
+        sigma = numerator / torch.clamp(denominator, 1e-20)  # nfrmes, nloc
         u = (sigma - self.sw_rmin) / (self.sw_rmax - self.sw_rmin)
         coef = torch.zeros_like(u)
         left_mask = sigma < self.sw_rmin
diff --git a/source/tests/pt/model/test_null_input.py b/source/tests/pt/model/test_null_input.py
index c8f4307d52..d5cf2475fb 100644
--- a/source/tests/pt/model/test_null_input.py
+++ b/source/tests/pt/model/test_null_input.py
@@ -125,7 +125,6 @@ def setUp(self):
         self.model = get_model(model_params).to(env.DEVICE)
 
 
-@unittest.skip("FAILED at the moment")
 class TestEnergyModelZBL(unittest.TestCase, NullTest):
     def setUp(self):
         model_params = copy.deepcopy(model_zbl)