diff --git a/accim/funcs_for_besos/param_accis.py b/accim/funcs_for_besos/param_accis.py
index 399b6db7..9176cdae 100644
--- a/accim/funcs_for_besos/param_accis.py
+++ b/accim/funcs_for_besos/param_accis.py
@@ -338,7 +338,7 @@ def modify_MaxWindSpeed(idf, value):
 def modify_ASTtol(idf, value):
     SetInputData = ([program for program in idf.idfobjects['EnergyManagementSystem:Program'] if
                      program.Name == 'SetInputData'][0])
-    SetInputData.Program_Line_9 = f'set ACSTtol = {value}'
+    SetInputData.Program_Line_9 = f'set ACSTtol = {-value}'
     SetInputData.Program_Line_10 = f'set AHSTtol = {value}'
     return