diff --git a/particle_tracking_manager/the_manager.py b/particle_tracking_manager/the_manager.py
index da35c6d..7a1b017 100644
--- a/particle_tracking_manager/the_manager.py
+++ b/particle_tracking_manager/the_manager.py
@@ -164,6 +164,7 @@ class ParticleTrackingManager:
     seed_seafloor: bool
     output_file: str
     output_format: str
+    output_file_initial: Optional[str]
 
     def __init__(
         self,
@@ -223,6 +224,8 @@ def __init__(
         self.__dict__["has_run_seeding"] = False
         self.__dict__["has_run"] = False
 
+        self.output_file_initial = None
+
         # Set all attributes which will trigger some checks and changes in __setattr__
         # these will also update "value" in the config dict
         for key in sig.parameters.keys():
@@ -383,9 +386,10 @@ def __setattr__(self, name: str, value) -> None:
                     )
 
                 # make new attribute for initial output file
-                self.output_file_initial = str(
-                    pathlib.Path(f"{output_file}_initial").with_suffix(".nc")
-                )
+                if self.output_file_initial is None:
+                    self.output_file_initial = str(
+                        pathlib.Path(f"{output_file}_initial").with_suffix(".nc")
+                    )
 
                 if self.output_format is not None:
                     if self.output_format == "netcdf":