diff --git a/da/tm5/model.py b/da/tm5/model.py
index 682143c361feedfeb7e93c85336418065e3cb548..d6fe2e82814e8bbbd2de80674d7caf660dd7af0f 100755
--- a/da/tm5/model.py
+++ b/da/tm5/model.py
@@ -339,8 +339,12 @@ def DaInitialize(rc_da_shell):
                 'das.input.dir' : rc_da_shell['dir.input']
                 }
 
-    if rc_da_shell['time.restart'] or rc_da_shell['time.sample.start'] != rc_da_shell['time.start']: 
+    if rc_da_shell['time.restart']:  # If this is a restart from a previous cycle, the TM5 model should do a restart
         NewItems['istart'] = 3
+    if rc_da_shell['time.sample.window'] != 0:  # If this is a restart from a previous time step wihtin the filter lag, the TM5 model should do a restart
+        NewItems['istart'] = 3
+    
+    # If neither one is true, simply take the istart value from the tm5.rc file that was read
 
     Tm5Model.ModifyRC(NewItems)