diff --git a/src/inference_base.py b/src/inference_base.py
index ecf266c..3df7592 100644
--- a/src/inference_base.py
+++ b/src/inference_base.py
@@ -139,18 +139,19 @@ def get_native(pdb_path):
     valid_atoms_mask = np.zeros(len(structure), dtype=bool)
 
     # Iterate over unique residues
-    for res_id in set(structure.res_id):
-        # Create a mask for atoms in the current residue
-        residue_mask = (structure.res_id == res_id)
-        residue_atoms = structure[residue_mask]
+    for chain_id in set(structure.chain_id):
+        for res_id in set(structure.res_id):
+            # Create a mask for atoms in the current residue
+            residue_mask = ((structure.res_id == res_id) & (structure.chain_id == chain_id))
+            residue_atoms = structure[residue_mask]
         
-        # Get atom names for this residue
-        residue_atom_names = set(residue_atoms.atom_name)
-        
-        # Check if all backbone atoms are present
-        if backbone_atoms.issubset(residue_atom_names):
-            # If backbone atoms are present, mark this residue as valid
-            valid_atoms_mask[residue_mask] = True
+            # Get atom names for this residue
+            residue_atom_names = set(residue_atoms.atom_name)
+            
+            # Check if all backbone atoms are present
+            if backbone_atoms.issubset(residue_atom_names):
+                # If backbone atoms are present, mark this residue as valid
+                valid_atoms_mask[residue_mask] = True
 
     # Apply the mask to filter the structure
     filtered_structure = structure[valid_atoms_mask]