diff --git a/kratos/python_scripts/json_output_process.py b/kratos/python_scripts/json_output_process.py
index a7680cbf73cb..f129fe1a7c3a 100644
--- a/kratos/python_scripts/json_output_process.py
+++ b/kratos/python_scripts/json_output_process.py
@@ -2,6 +2,9 @@
 import KratosMultiphysics
 from KratosMultiphysics.json_utilities import read_external_json, write_external_json
 
+# Adding operator add
+from operator import add
+
 def Factory(settings, Model):
     if not isinstance(settings, KratosMultiphysics.Parameters):
         raise Exception("Expected input shall be a Parameters object, encapsulating a json string")
@@ -285,16 +288,16 @@ def ExecuteFinalizeSolutionStep(self):
                                             data["RESULTANT"][variable_name + "_Z"][-1] += value[2]
                                 else:
                                     if not self.resultant_solution:
-                                        list = self.__kratos_vector_to_python_list(value)
-                                        data[node_identifier][variable_name ].append(list)
+                                        lst = self.__kratos_vector_to_python_list(value)
+                                        data[node_identifier][variable_name ].append(lst)
                                     else:
                                         aux = 0.0
                                         for index in range(len(value)):
                                             aux += value[index]
                                         if count == 0:
-                                            data["RESULTANT"][variable_name ].append(aux)
+                                            data["RESULTANT"][variable_name].append(aux)
                                         else:
-                                            data["RESULTANT"][variable_name ][-1] += aux
+                                            data["RESULTANT"][variable_name][-1] += aux
                             elif variable_type == "Vector":
                                 if not self.resultant_solution:
                                     data[node_identifier][variable_name].append(self.__kratos_vector_to_python_list(value))
@@ -302,7 +305,7 @@ def ExecuteFinalizeSolutionStep(self):
                                     if count == 0:
                                         data["RESULTANT"][variable_name].append(self.__kratos_vector_to_python_list(value))
                                     else:
-                                        data["RESULTANT"][variable_name][-1] += self.__kratos_vector_to_python_list(value)
+                                        data["RESULTANT"][variable_name][-1] = list(map(add, data["RESULTANT"][variable_name][-1], self.__kratos_vector_to_python_list(value)))
 
                             # TODO: Add pending classes
                         count += 1
@@ -352,9 +355,9 @@ def ExecuteFinalizeSolutionStep(self):
                                                 data["RESULTANT"][variable_name + "_Z"][str(gp)][-1] += value[gp][2]
                                 else:
                                     if not self.resultant_solution:
-                                        list = self.__kratos_vector_to_python_list(value)
+                                        lst = self.__kratos_vector_to_python_list(value)
                                         for gp in range(gauss_point_number):
-                                            data["ELEMENT_" + str(elem.Id)][variable_name][str(gp)].append(list)
+                                            data["ELEMENT_" + str(elem.Id)][variable_name][str(gp)].append(lst)
                                     else:
                                         if count == 0:
                                             for gp in range(gauss_point_number):
@@ -371,13 +374,13 @@ def ExecuteFinalizeSolutionStep(self):
                             elif variable_type == "Vector":
                                 if not self.resultant_solution:
                                     for gp in range(gauss_point_number):
-                                        list = self.__kratos_vector_to_python_list(value[gp])
-                                        data["ELEMENT_" + str(elem.Id)][variable_name][str(gp)].append(list)
+                                        lst = self.__kratos_vector_to_python_list(value[gp])
+                                        data["ELEMENT_" + str(elem.Id)][variable_name][str(gp)].append(lst)
                                 else:
                                     if count == 0:
                                         for gp in range(gauss_point_number):
-                                            list = self.__kratos_vector_to_python_list(value[gp])
-                                            data["RESULTANT"][variable_name][str(gp)][-1] += list
+                                            lst = self.__kratos_vector_to_python_list(value[gp])
+                                            data["RESULTANT"][variable_name][str(gp)][-1] += lst
 
                                 # TODO: Add pending classes
                     count += 1
@@ -392,10 +395,10 @@ def __kratos_vector_to_python_list(self, value):
         value -- The Kratos vector to transform
         """
 
-        list = []
+        lst = []
         for index in range(len(value)):
-            list.append(value[index])
-        return list
+            lst.append(value[index])
+        return lst
 
     def __generate_variable_list_from_input(self, param):
         """ Parse a list of variables from input.
diff --git a/kratos/tests/test_json_output_process.py b/kratos/tests/test_json_output_process.py
index 51f0f900977e..280a733bcb3b 100644
--- a/kratos/tests/test_json_output_process.py
+++ b/kratos/tests/test_json_output_process.py
@@ -1,11 +1,14 @@
 import KratosMultiphysics
 import KratosMultiphysics.KratosUnittest as KratosUnittest
+import KratosMultiphysics.kratos_utilities as KratosUtils
 from KratosMultiphysics.json_output_process import JsonOutputProcess
 
-import itertools
 import json
+import os
 from pathlib import Path
 
+def GetFilePath(fileName):
+    return os.path.join(os.path.dirname(os.path.realpath(__file__)), fileName)
 
 class TestJsonOutputProcess(KratosUnittest.TestCase):
     def setUp(self):
@@ -13,6 +16,10 @@ def setUp(self):
         self.model = KratosMultiphysics.Model()
         self.model_part = self.model.CreateModelPart("Main")
 
+    def tearDown(self):
+        KratosUtils.DeleteFileIfExisting(GetFilePath("external_forces_output.json"))
+        KratosUtils.DeleteFileIfExisting(GetFilePath("resultant_external_forces_output.json"))
+
     def add_three_nodes_to_model_part(self):
         node_ids_and_coordinates = [
             (1, 0.0, 0.0, 0.0),
@@ -79,6 +86,7 @@ def test_output_of_resultant_vector_variable(self):
         self.add_vectors_to_nodes_of_model_part(
             vector_variable_for_testing, test_vectors
         )
+        ref_solution = [6.0, 6.0, 6.0]
 
         output_file_path = (
             Path(__file__).resolve().parent / "resultant_external_forces_output.json"
@@ -103,7 +111,7 @@ def test_output_of_resultant_vector_variable(self):
         self.assertEqual(len(resultant_vector_variable_results_for_all_time_steps), 1)
         self.assertVectorAlmostEqual(
             resultant_vector_variable_results_for_all_time_steps[0],
-            list(itertools.chain(*test_vectors)),
+            ref_solution,
         )