diff --git a/python/swiftest/swiftest/simulation_class.py b/python/swiftest/swiftest/simulation_class.py
index 7669c774f..aeedc8ac6 100644
--- a/python/swiftest/swiftest/simulation_class.py
+++ b/python/swiftest/swiftest/simulation_class.py
@@ -41,7 +41,7 @@ class Simulation:
     This is a class that defines the basic Swift/Swifter/Swiftest simulation object
     """
 
-    def __init__(self,read_param: bool = False, **kwargs: Any):
+    def __init__(self,read_param: bool = False, read_old_output_file: bool = False, **kwargs: Any):
         """
 
         Parameters
@@ -64,6 +64,10 @@ def __init__(self,read_param: bool = False, **kwargs: Any):
                 - The argument has an equivalent parameter or set of parameters in the parameter input file.
             3. Default values (see below)
 
+        read_old_output_file : bool, default False
+            If true, read in a pre-existing binary input file given by the argument `output_file_name` if it exists.
+            Parameter input file equivalent: None
+
         **kwargs : See list of valid parameters and their defaults below
 
         codename : {"Swiftest", "Swifter", "Swift"}, default "Swiftest"
@@ -140,9 +144,6 @@ def __init__(self,read_param: bool = False, **kwargs: Any):
             Specifies the format for the data saved to the output file. If "XV" then cartesian position and velocity
             vectors for all bodies are stored. If "XVEL" then the orbital elements are also stored.
             Parameter input file equivalent: `OUT_FORM`
-        read_old_output_file : bool, default False
-            If true, read in a pre-existing binary input file given by the argument `output_file_name` if it exists.
-            Parameter input file equivalent: None
         MU : str, default "MSUN"
             The mass unit system to use. Case-insensitive valid options are:
             * "Msun"   : Solar mass
@@ -320,9 +321,9 @@ def __init__(self,read_param: bool = False, **kwargs: Any):
         # Higher Priority: Values from a file (if requested and it exists)
         #-----------------------------------------------------------------
 
-        # If the user asks to read in an old parameter file, override any default parameters with values from the file
+        # If the user asks to read in an old parameter file or output file, override any default parameters with values from the file
         # If the file doesn't exist, flag it for now so we know to create it
-        if read_param:
+        if read_param or read_old_output_file:
             #good_param is self.read_param()
             if self.read_param():
                 # We will add the parameter file to the kwarg list. This will keep the set_parameter method from
@@ -344,7 +345,6 @@ def __init__(self,read_param: bool = False, **kwargs: Any):
             self.write_param()
 
         # Read in an old simulation file if requested
-        read_old_output_file = kwargs.pop("read_old_output_file",False)
         if read_old_output_file:
             binpath = os.path.join(self.sim_dir, self.param['BIN_OUT'])
             if os.path.exists(binpath):