diff --git a/mdevaluate/coordinates.py b/mdevaluate/coordinates.py
index fb99b93..c976e2d 100755
--- a/mdevaluate/coordinates.py
+++ b/mdevaluate/coordinates.py
@@ -551,7 +551,7 @@ def pore_coordinates(coordinates, origin, sym_axis="z"):
 
 
 @map_coordinates
-def vectors(coordinates, atoms_a, atoms_b, normed=False, box=None):
+def vectors(coordinates, atoms_a, atoms_b, normed=False):
     """
     Compute the vectors between the atoms of two subsets.
 
@@ -580,6 +580,7 @@ def vectors(coordinates, atoms_a, atoms_b, normed=False, box=None):
             coords[6] - (coords[7] + coords[8])/2,
         ])
     """
+    box = coordinates.box
     coords_a = coordinates[atoms_a]
     if len(coords_a.shape) > 2:
         coords_a = coords_a.mean(axis=0)