diff --git a/sot/opcode_translator/executor/opcode_executor.py b/sot/opcode_translator/executor/opcode_executor.py
index bc82f051c..7c79023f9 100644
--- a/sot/opcode_translator/executor/opcode_executor.py
+++ b/sot/opcode_translator/executor/opcode_executor.py
@@ -422,7 +422,7 @@ def __init__(self, code: types.CodeType, graph: FunctionGraph):
         self._code = code
         self._instructions = get_instructions(self._code)
         self._graph = graph
-        self._current_line: int | None = None
+        self._current_line: int = -1
         self.new_code: types.CodeType | None = None
         self.guard_fn = None
         self._name = "Executor"
@@ -527,15 +527,16 @@ def error_message_summary(original_error: Exception) -> str:
         message_lines = ["In simulate execution:", ""]
         for current_simulator in OpcodeExecutorBase.call_stack:
             code = current_simulator._code
-            current_line = current_simulator._current_line or 0
+            current_line = current_simulator._current_line
             lines, start = inspect.getsourcelines(code)
             real_name = code.co_name
             message_lines.append(
                 f"{indent}  File \"{code.co_filename}\", line {current_line}, in {real_name}"
             )
-            message_lines.append(
-                f"{indent}  {lines[current_line-start].rstrip()}"
-            )
+            if current_line != -1:
+                message_lines.append(
+                    f"{indent}  {lines[current_line-start].rstrip()}"
+                )
         error_message = traceback.format_exception_only(
             type(original_error), original_error
         )
diff --git a/sot/opcode_translator/executor/side_effects.py b/sot/opcode_translator/executor/side_effects.py
index 9494dfe7e..9c71571f6 100644
--- a/sot/opcode_translator/executor/side_effects.py
+++ b/sot/opcode_translator/executor/side_effects.py
@@ -39,8 +39,8 @@ def get_proxy(
 
     def get_state(self):
         return SideEffectsState(
-            self.data_id_to_proxy,
-            self.variables,
+            self.data_id_to_proxy.copy(),
+            self.variables.copy(),
             [proxy.version for proxy in self.data_id_to_proxy.values()],
         )
 
diff --git a/sot/opcode_translator/instruction_utils/instruction_utils.py b/sot/opcode_translator/instruction_utils/instruction_utils.py
index e1aa77b86..8a2c67759 100644
--- a/sot/opcode_translator/instruction_utils/instruction_utils.py
+++ b/sot/opcode_translator/instruction_utils/instruction_utils.py
@@ -254,7 +254,7 @@ def calc_offset_from_bytecode_offset(bytecode_offset: int) -> int:
 
 def replace_instr(instructions, instr, new_instr):
     idx = instructions.index(instr)
-    instructions[idx, idx + 1] = new_instr
+    instructions[idx : idx + 1] = new_instr
 
 
 def instrs_info(instrs, mark=None):