diff --git a/pysisyphus/calculators/CFOUR.py b/pysisyphus/calculators/CFOUR.py
index b2c9d7ff5..f1354aab2 100644
--- a/pysisyphus/calculators/CFOUR.py
+++ b/pysisyphus/calculators/CFOUR.py
@@ -133,6 +133,7 @@ def __init__(
         self.gradient_fn = "GRD"
         self.to_keep = ("out.log", "density:__den.dat", "mos:NEWMOS")
         self.initden = None
+        self.mos = None
         self.wavefunction_dump = wavefunction_dump
 
         if self.wavefunction_dump:
@@ -161,7 +162,7 @@ def prepare(self, inp):
         path = super().prepare(inp)
         if self.initden:
             shutil.copy(self.initden, f"{path}/initden.dat")
-        if self.oldmos:
+        if self.mos:
             shutil.copy(self.mos, f"{path}/OLDMOS")
         return path