diff --git a/mrdna/readers/segmentmodel_from_oxdna_pinyi.py b/mrdna/readers/segmentmodel_from_oxdna_pinyi.py
index 9dcbbd1837515459defebbc91400031fef87d097..2f030240dcc75cd7480de157bbaa24a7fe095722 100644
--- a/mrdna/readers/segmentmodel_from_oxdna_pinyi.py
+++ b/mrdna/readers/segmentmodel_from_oxdna_pinyi.py
@@ -127,7 +127,7 @@ def mrdna_model_from_oxdna(coordinate_file, topology_file,virt2nuc=None,get_nt_p
         
         non_stack_ind,=np.where(nt_prop["stack"]==-1)
         for i in non_stack_ind:
-            zid=int(nt_prop.loc[i][zid])+int(nt_prop.loc[i]["fwd"])*2-1
+            zid=int(nt_prop.loc[i]["zid"])+int(nt_prop.loc[i]["fwd"])*2-1
             try:
                 nt_prop["stack"][i]=bp_map[(nt_prop.loc[i]["vh"],str(zid),nt_prop.loc[i]["fwd"])]
             except:
diff --git a/mrdna/readers/segmentmodel_from_scadnano.py b/mrdna/readers/segmentmodel_from_scadnano.py
index 863a61b45a226e3ff9f5a3c8e3f3e8445c8ca66c..f47b9d3bbcb683e75448d9f335aad792404680b6 100644
--- a/mrdna/readers/segmentmodel_from_scadnano.py
+++ b/mrdna/readers/segmentmodel_from_scadnano.py
@@ -122,7 +122,7 @@ def gen_prop_table(fname):
     nt_prop["bp"]=bp
     non_stack_ind,=np.where(nt_prop["stack"]==-1)
     for i in non_stack_ind:
-        zid=int(nt_prop.loc[i][zid])+int(nt_prop.loc[i]["fwd"])*2-1
+        zid=int(nt_prop.loc[i]["zid"])+int(nt_prop.loc[i]["fwd"])*2-1
         try:
             nt_prop["stack"][i]=bp_map[(nt_prop.loc[i]["vh"],str(zid),nt_prop.loc[i]["fwd"])]
         except: