diff --git a/src/gui_qt/main/management.py b/src/gui_qt/main/management.py
index 2f87e87..62f3cb9 100644
--- a/src/gui_qt/main/management.py
+++ b/src/gui_qt/main/management.py
@@ -1189,10 +1189,10 @@ class UpperManagement(QtCore.QObject):
         y = np.zeros(_x.size)
 
         for i in range(_x.size):
-            _x[i] = sd.convert(_x[i], *sd_param[i], from_=opts['tau_type'], to_='raw')
+            _x_i = sd.convert(_x[i], *sd_param[i], from_=opts['tau_type'], to_='raw')
             relax.dist_parameter = sd_param[i]
             relax.set_coupling(opts['coup'], parameter=cp_param[i], keywords=opts['cp_param'][1])
-            y[i] = relax_func(x2, _x[i])
+            y[i] = relax_func(x2, _x_i)
 
         pts = Points(x1, y, name=sd.name)
         pts.meta.update(opts)