diff --git a/janus_core/calculations/geom_opt.py b/janus_core/calculations/geom_opt.py
index 55c68637..6db16e80 100644
--- a/janus_core/calculations/geom_opt.py
+++ b/janus_core/calculations/geom_opt.py
@@ -239,13 +239,10 @@ def __init__(
         ).absolute()
 
         if self.write_traj:
-            if "filename" not in self.traj_kwargs:
-                self.traj_kwargs["filename"] = self._build_filename(
-                    "traj.extxyz"
-                ).absolute()
-            if "trajectory" not in self.opt_kwargs:
-                # Overwrite .traj binary with .extxyz by default.
-                self.opt_kwargs["trajectory"] = str(self.traj_kwargs["filename"])
+            self.traj_kwargs.setdefault(
+                "filename", self._build_filename("traj.extxyz").absolute()
+            )
+            self.opt_kwargs.setdefault("trajectory", str(self.traj_kwargs["filename"]))
         elif self.traj_kwargs:
             raise ValueError("traj_kwargs given, but trajectory writing not enabled.")
         elif "trajectory" in self.opt_kwargs:
diff --git a/janus_core/cli/geomopt.py b/janus_core/cli/geomopt.py
index d92e9e4b..4adb89bd 100644
--- a/janus_core/cli/geomopt.py
+++ b/janus_core/cli/geomopt.py
@@ -44,11 +44,8 @@ def _set_minimize_kwargs(
         Scalar pressure when optimizing cell geometry, in GPa. Passed to the filter
         function if either `opt_cell_lengths` or `opt_cell_fully` is True.
     """
-    if "opt_kwargs" not in minimize_kwargs:
-        minimize_kwargs["opt_kwargs"] = {}
-
-    if "traj_kwargs" not in minimize_kwargs:
-        minimize_kwargs["traj_kwargs"] = {}
+    minimize_kwargs.setdefault("opt_kwargs", {})
+    minimize_kwargs.setdefault("traj_kwargs", {})
 
     # Check hydrostatic_strain and scalar pressure not duplicated
     if "filter_kwargs" in minimize_kwargs: