diff --git a/mrdna/segmentmodel.py b/mrdna/segmentmodel.py
index 1512a7b033f814dc790aed39fcd4eba1af3fe0b9..fd93c77554ec173c4865bc65e90fae131e34a643 100644
--- a/mrdna/segmentmodel.py
+++ b/mrdna/segmentmodel.py
@@ -1557,7 +1557,7 @@ class SegmentModel(ArbdModel):
         self.DEBUG = DEBUG
         if DEBUG > 0: print("Building ARBD Model")
         ArbdModel.__init__(self,segments,
-                           origin, dimensions,
+                           dimensions, origin,
                            temperature, timestep, cutoff,
                            decompPeriod, pairlistDistance=None,
                            nonbondedResolution = 0,