diff --git a/arkane/ess/orca.py b/arkane/ess/orca.py
index a97b78fe44..4ca1cece5a 100644
--- a/arkane/ess/orca.py
+++ b/arkane/ess/orca.py
@@ -116,7 +116,7 @@ def load_force_constant_matrix(self):
         for (_, _, files) in os.walk(os.path.dirname(self.path)):
             for file_ in files:
                 if file_.endswith('.hess'):
-                    hess_files.append(file_)
+                    hess_files.append(os.path.join(os.path.dirname(self.path), file_))
             break
         if len(hess_files) == 1:
             hess_file = hess_files[0]