diff --git a/src/utils/regress.py b/src/utils/regress.py
index ab07cfc133a49f65ddadb13dc71f81d7f5459c03..2a8ec27970ceb1cfaecf97ecdee5f10bf9cfffed 100644
--- a/src/utils/regress.py
+++ b/src/utils/regress.py
@@ -173,7 +173,10 @@ class TpeIpls(Regmodel):
 
         ### Preprocessing
         x0 = [self._xc, self._xt]
-        x1 = [eval(str(params['normalization'])+"(x0[i])") for i in range(2)]
+        # x1 = [eval(str(params['normalization'])+"(x0[i])") for i in range(2)]
+        x1 = []
+        x1.append(eval(str(params['normalization'])+'(x0[0])'))
+        x1.append(eval(str(params['normalization'])+'(x0[1])'))
 
         a, b, c = params['deriv'], params['polyorder'], params['window_length']
         if a > b or b > c: