diff --git a/python/swiftest/swiftest/simulation_class.py b/python/swiftest/swiftest/simulation_class.py
index 8c9ecbc7b..47be96e75 100644
--- a/python/swiftest/swiftest/simulation_class.py
+++ b/python/swiftest/swiftest/simulation_class.py
@@ -55,15 +55,18 @@ def __init__(self, codename="Swiftest", param_file="", readbin=True):
         }
         self.codename = codename
         if param_file != "" :
+            dir_path = os.path.dirname(os.path.realpath(param_file))
             self.read_param(param_file, codename)
             if readbin:
                 if os.path.exists(self.param['BIN_OUT']):
                     self.bin2xr()
+                elif os.path.exists(dir_path + '/' + self.param['BIN_OUT']):
+                    self.param['BIN_OUT'] = dir_path + '/' + self.param['BIN_OUT']
+                    self.bin2xr()
                 else:
                     print(f"BIN_OUT file {self.param['BIN_OUT']} not found.")
         return
     
-    
     def add(self, plname, date=date.today().isoformat(), idval=None):
         """
         Adds a solar system body to an existing simulation DataSet.