diff --git a/kan/utils.py b/kan/utils.py
index ef06abca..7a029a82 100644
--- a/kan/utils.py
+++ b/kan/utils.py
@@ -200,13 +200,13 @@ def fit_params(x, y, fun, a_range=(-10,10), b_range=(-10,10), grid_number=101, i
             if _ == 0 and verbose==True:
                 print('Best value at boundary.')
             if a_id == 0:
-                a_arange = [a_[0], a_[1]]
+                a_range = [a_[0], a_[1]]
             if a_id == grid_number - 1:
-                a_arange = [a_[-2], a_[-1]]
+                a_range = [a_[-2], a_[-1]]
             if b_id == 0:
-                b_arange = [b_[0], b_[1]]
+                b_range = [b_[0], b_[1]]
             if b_id == grid_number - 1:
-                b_arange = [b_[-2], b_[-1]]
+                b_range = [b_[-2], b_[-1]]
             
         else:
             a_range = [a_[a_id-1], a_[a_id+1]]
@@ -255,4 +255,4 @@ def add_symbolic(name, fun):
     '''
     exec(f"globals()['{name}'] = sympy.Function('{name}')")
     SYMBOLIC_LIB[name] = (fun, globals()[name])
-    
\ No newline at end of file
+