diff --git a/segmentmodel.py b/segmentmodel.py
index a26496b39ce3404731ae163dd14dc9b58e1443b7..684024f20fdaba89110f2e4b9bcdd402cf3e8f17 100644
--- a/segmentmodel.py
+++ b/segmentmodel.py
@@ -1790,7 +1790,7 @@ class SegmentModel(ArbdModel):
                     o = b1.orientation_bead
                     pot = self.get_angle_potential(k,t0)
                     self.add_angle( o,b1,b2, pot )
-                else:
+                if 'orientation_bead' in b2.__dict__:
                     t0 = 150
                     if B.on_fwd_strand: t0 = 30
                     o = b2.orientation_bead