diff --git a/src/legendoptics/nylon.py b/src/legendoptics/nylon.py
index 0cc160f..cccf89e 100644
--- a/src/legendoptics/nylon.py
+++ b/src/legendoptics/nylon.py
@@ -5,7 +5,7 @@
     In: Astroparticle Physics 97 (2018). https://doi.org/10.1016/j.astropartphys.2017.10.003
 
 .. [Benziger2007] J. Benziger et al. “The Nylon Scintillator Containment Vessels for the
-    Borexino Solar Neutrino Experiment” In: nternational Journal of Modern Physics A, 29(16)
+    Borexino Solar Neutrino Experiment” In: International Journal of Modern Physics A, 29(16)
     (2014). https://doi.org/10.1016/j.nima.2007.08.176
 """
 
diff --git a/src/legendoptics/pyg4utils.py b/src/legendoptics/pyg4utils.py
index 0f746db..68375e0 100644
--- a/src/legendoptics/pyg4utils.py
+++ b/src/legendoptics/pyg4utils.py
@@ -106,6 +106,8 @@ def _val_pint_to_gdml(v):
     def addVecPropertyPint(self, name, e, v):  # noqa: N802
         vunit, v = _val_pint_to_gdml(v)
         eunit, e = _val_pint_to_gdml(e)
+        v = np.array(v)
+        e = np.array(e)
 
         if name in length_props and vunit not in length_u:
             log.warning("Wrong unit %s for property %s", vunit, name)
@@ -114,7 +116,10 @@ def addVecPropertyPint(self, name, e, v):  # noqa: N802
         if eunit not in ["", "eV", "keV", "MeV", "GeV", "TeV", "PeV"]:
             log.warning("Wrong energy unit %s", eunit)
 
-        # TODO: necessary to reorder values
+        # reorder the values to be in ascending energy order.
+        sort = np.argsort(e)
+        e = e[sort]
+        v = v[sort]
 
         return g4.Material.addVecProperty(self, name, e, v, eunit, vunit)