diff --git a/CanonicalNucleotideAtoms.py b/CanonicalNucleotideAtoms.py
index 9f9c5415463ad6416dab095adf79d2d05326bea4..e8403c05c78dcd2523bbee1d90e17d8d3467e47f 100644
--- a/CanonicalNucleotideAtoms.py
+++ b/CanonicalNucleotideAtoms.py
@@ -72,14 +72,14 @@ class CanonicalNucleotideFactory(Group):
         b = self.bonds
         a = self.angles
         d = self.dihedrals
-        i = self.impropers
+        imp = self.impropers
         for i,j in zip(b[::2],b[1::2]):
             nt.add_bond( atoms[i], atoms[j], None )
         for i,j,k in zip(a[::3],a[1::3],a[2::3]):
             nt.add_angle( atoms[i], atoms[j], atoms[k], None )
         for i,j,k,l in zip(d[::4],d[1::4],d[2::4],d[3::4]):
             nt.add_dihedral( atoms[i], atoms[j], atoms[k], atoms[l], None )
-        for i,j,k,l in zip(d[::4],d[1::4],d[2::4],d[3::4]):
+        for i,j,k,l in zip(imp[::4],imp[1::4],imp[2::4],imp[3::4]):
             nt.add_improper( atoms[i], atoms[j], atoms[k], atoms[l], None )
         return nt
 
diff --git a/arbdmodel.py b/arbdmodel.py
index d92f235c7e18359de8c347e95e1329a02a1e2d31..61e3d86e10e88ad8d549883c2f903137fa0cea0d 100644
--- a/arbdmodel.py
+++ b/arbdmodel.py
@@ -506,6 +506,8 @@ class PdbModel(Transformable, Parent):
                 if counter == 4:
                     fh.write("\n")
                     counter = 0
+                else:
+                    fh.write(" ")
             fh.write("\n")
 
             ## Write out angles
@@ -518,6 +520,8 @@ class PdbModel(Transformable, Parent):
                 if counter == 3:
                     fh.write("\n")
                     counter = 0
+                else:
+                    fh.write(" ")
             fh.write("\n")
 
             ## Write out dihedrals
@@ -530,6 +534,8 @@ class PdbModel(Transformable, Parent):
                 if counter == 2:
                     fh.write("\n")
                     counter = 0
+                else:
+                    fh.write(" ")
             fh.write("\n")
 
             ## Write out impropers
@@ -542,6 +548,8 @@ class PdbModel(Transformable, Parent):
                 if counter == 2:
                     fh.write("\n")
                     counter = 0
+                else:
+                    fh.write(" ")
             fh.write("\n")