diff --git a/pyproject.toml b/pyproject.toml
index fc3343fe9..d8c4f3e5f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -44,6 +44,7 @@ target-version = "py38"
 "tests/library/test_loaders.py" = ["N802", "N803"]
 "tests/library/test_dataclass.py" = ["F811"]
 "src/unitxt/validate.py" = ["B024"]
+"src/unitxt/standard.py" = ["C901"]
 "src/unitxt/type_utils.py" = ["C901"]
 "src/unitxt/dataclass.py" = ["C901"]
 "src/unitxt/operators.py" = ["C901"]
diff --git a/src/unitxt/standard.py b/src/unitxt/standard.py
index 857ea8ddd..5f7cfba4d 100644
--- a/src/unitxt/standard.py
+++ b/src/unitxt/standard.py
@@ -187,6 +187,11 @@ def produce(self, task_instances):
         return list(multi_stream["__inference__"])
 
     def prepare(self):
+        # To avoid the Python's mutable default list trap, we set the default value to None
+        # and then set it to an empty list if it is None.
+        if self.card.preprocess_steps is None:
+            self.card.preprocess_steps = []
+
         self.set_pipelines()
 
         loader = self.card.loader