diff --git a/bec_widgets/widgets/control/device_input/device_combobox/device_combobox.py b/bec_widgets/widgets/control/device_input/device_combobox/device_combobox.py
index 1700b3e1..9ebffa4e 100644
--- a/bec_widgets/widgets/control/device_input/device_combobox/device_combobox.py
+++ b/bec_widgets/widgets/control/device_input/device_combobox/device_combobox.py
@@ -496,6 +496,7 @@ class DeviceComboBox(BECWidget, QComboBox):
         """Cleanup the widget."""
         if self._callback_id is not None:
             self.bec_dispatcher.client.callbacks.remove(self._callback_id)
+            self._callback_id = None
         super().cleanup()
 
     def get_current_device(self) -> object:
diff --git a/bec_widgets/widgets/control/device_input/signal_combobox/signal_combobox.py b/bec_widgets/widgets/control/device_input/signal_combobox/signal_combobox.py
index 89478694..03dc0836 100644
--- a/bec_widgets/widgets/control/device_input/signal_combobox/signal_combobox.py
+++ b/bec_widgets/widgets/control/device_input/signal_combobox/signal_combobox.py
@@ -588,7 +588,9 @@ class SignalComboBox(BECWidget, QComboBox):
 
     def cleanup(self):
         """Cleanup the widget."""
-        self.bec_dispatcher.client.callbacks.remove(self._device_update_register)
+        if self._device_update_register is not None:
+            self.bec_dispatcher.client.callbacks.remove(self._device_update_register)
+            self._device_update_register = None
         super().cleanup()
 
     @staticmethod
diff --git a/tests/unit_tests/test_device_input_widgets.py b/tests/unit_tests/test_device_input_widgets.py
index 78763071..b5927c5e 100644
--- a/tests/unit_tests/test_device_input_widgets.py
+++ b/tests/unit_tests/test_device_input_widgets.py
@@ -1,3 +1,5 @@
+from unittest import mock
+
 import pytest
 from bec_lib.device import ReadoutPriority
 
@@ -124,6 +126,19 @@ def test_device_input_combobox_disabled_invalid_has_neutral_border(device_input_
     assert "red" in device_input_combobox.styleSheet()
 
 
+def test_device_input_combobox_cleanup_unregisters_callback(qtbot, mocked_client):
+    with mock.patch.object(mocked_client.callbacks, "remove"):
+        widget = DeviceComboBox(client=mocked_client)
+        qtbot.addWidget(widget)
+        callback_id = widget._callback_id
+
+        widget.close()
+        widget.deleteLater()
+
+        mocked_client.callbacks.remove.assert_called_once_with(callback_id)
+        assert widget._callback_id is None
+
+
 def test_get_device_from_input_combobox_init(device_input_combobox):
     device_input_combobox.setCurrentIndex(0)
     device_text = device_input_combobox.currentText()
diff --git a/tests/unit_tests/test_device_signal_input.py b/tests/unit_tests/test_device_signal_input.py
index 836e3f4e..743a8140 100644
--- a/tests/unit_tests/test_device_signal_input.py
+++ b/tests/unit_tests/test_device_signal_input.py
@@ -188,10 +188,12 @@ def test_linked_device_combobox_updates_signal_combobox_on_each_text_change(
 def test_device_signal_input_base_cleanup(qtbot, mocked_client):
     with mock.patch.object(mocked_client.callbacks, "remove"):
         widget = SignalComboBox(client=mocked_client)
+        callback_id = widget._device_update_register
         widget.close()
         widget.deleteLater()
 
-        mocked_client.callbacks.remove.assert_called_once_with(widget._device_update_register)
+        mocked_client.callbacks.remove.assert_called_once_with(callback_id)
+        assert widget._device_update_register is None
 
 
 def test_signal_combobox_get_signal_name_with_item_data(qtbot, device_signal_combobox):