diff --git a/mrdna/segmentmodel.py b/mrdna/segmentmodel.py
index 74c778231a517c5f6dd19f02abc75359872bfad9..5ccbe9311a21dcf7070d9c1fcda25ddd8e31a764 100644
--- a/mrdna/segmentmodel.py
+++ b/mrdna/segmentmodel.py
@@ -1690,8 +1690,7 @@ class SegmentModel(ArbdModel):
 
 
     def _getParent(self, *beads ):
-        if np.all( [b1.parent == b2.parent 
-                    for b1,b2 in zip(beads[:-1],beads[1:])] ):
+        if len(set([b.parent for b in beads])) == 1:
             return beads[0].parent
         else:
             return self