diff --git a/src/aiidalab_qe/app/submission/__init__.py b/src/aiidalab_qe/app/submission/__init__.py
index c90b057da..ab0a7a5e2 100644
--- a/src/aiidalab_qe/app/submission/__init__.py
+++ b/src/aiidalab_qe/app/submission/__init__.py
@@ -89,6 +89,7 @@ def __init__(self, qe_auto_setup=True, **kwargs):
         for _, entry_point in self.code_entries.items():
             for name, code in entry_point.items():
                 self.codes[name] = code
+                code.observe(self._update_state, "value")
                 self.code_children.append(self.codes[name])
         # set default codes
         self.set_selected_codes(DEFAULT_PARAMETERS["codes"])
diff --git a/tests/test_codes.py b/tests/test_codes.py
index b4f388cd1..0498fba04 100644
--- a/tests/test_codes.py
+++ b/tests/test_codes.py
@@ -44,6 +44,11 @@ def test_identify_submission_blockers(app):
     blockers = list(submit._identify_submission_blockers())
     assert len(blockers) == 1
     # set dos code to None, will introduce another blocker
+    dos_value = submit.codes["dos"].value
     submit.codes["dos"].value = None
     blockers = list(submit._identify_submission_blockers())
     assert len(blockers) == 2
+    # set dos code back will remove the blocker
+    submit.codes["dos"].value = dos_value
+    blockers = list(submit._identify_submission_blockers())
+    assert len(blockers) == 1