diff --git a/deepmd/fit/ener.py b/deepmd/fit/ener.py
index 2708aa7621..03145076cb 100644
--- a/deepmd/fit/ener.py
+++ b/deepmd/fit/ener.py
@@ -357,7 +357,9 @@ def build (self,
                                                 initializer = tf.constant_initializer(self.aparam_inv_std))
             
         inputs = tf.cast(tf.reshape(inputs, [-1, self.dim_descrpt * natoms[0]]), self.fitting_precision)
-        inputs_zero = tf.zeros_like(inputs, dtype=GLOBAL_TF_FLOAT_PRECISION)
+        if len(self.atom_ener):
+            # only for atom_ener
+            inputs_zero = tf.zeros_like(inputs, dtype=GLOBAL_TF_FLOAT_PRECISION)
         
 
         if bias_atom_e is not None :