diff --git a/ffprime/bond.py b/ffprime/bond.py
index cf4ef0c..5082803 100644
--- a/ffprime/bond.py
+++ b/ffprime/bond.py
@@ -28,6 +28,8 @@ def __init__(self, log_path="bonding/lig.log", fchk_path="bonding/lig.fchk"):
                 print("Eigenvectors are orthonormal.")
             else:
                 raise ValueError("Eigenvectors are not orthonormal.")
+        else:
+            self.hess_new = self.hess.copy()
 
         self.hess_new = (self.hess_new * 627.509391) / (0.529 ** 2)
         self.hess = (self.hess * 627.509391) / (0.529 ** 2)