diff --git a/src/backend/app/tasks/tasks_crud.py b/src/backend/app/tasks/tasks_crud.py
index 04be2bc57..c394fc64f 100644
--- a/src/backend/app/tasks/tasks_crud.py
+++ b/src/backend/app/tasks/tasks_crud.py
@@ -175,7 +175,10 @@ async def update_task_status(
 
 
 async def create_task_history_for_status_change(
-    db_task: db_models.DbTask, new_status: TaskStatus, db_user: db_models.DbUser, db
+    db_task: db_models.DbTask,
+    new_status: TaskStatus,
+    db_user: db_models.DbUser,
+    db: Session,
 ):
     """Append task status change to task history."""
     msg = (
diff --git a/src/backend/migrations/009-delete-user.sql b/src/backend/migrations/009-delete-user.sql
index af78a5e43..e414bd182 100644
--- a/src/backend/migrations/009-delete-user.sql
+++ b/src/backend/migrations/009-delete-user.sql
@@ -5,21 +5,85 @@
 BEGIN;
 
 -- Allow user_id in task_history to be NULL
-ALTER TABLE task_history
-ALTER COLUMN user_id DROP NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'task_history'
+        AND column_name = 'user_id'
+        AND is_nullable = 'NO'
+    ) THEN
+        ALTER TABLE task_history
+        ALTER COLUMN user_id DROP NOT NULL;
+    END IF;
+END $$;
 
 -- Add a new column username to task_history
-ALTER TABLE task_history
-ADD COLUMN username VARCHAR;
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'task_history'
+        AND column_name = 'username'
+    ) THEN
+        ALTER TABLE task_history
+        ADD COLUMN username VARCHAR;
+    END IF;
+END $$;
 
 -- Allow author_id in projects to be NULL
-ALTER TABLE projects ALTER COLUMN author_id DROP NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'projects'
+        AND column_name = 'author_id'
+        AND is_nullable = 'NO'
+    ) THEN
+        ALTER TABLE projects
+        ALTER COLUMN author_id DROP NOT NULL;
+    END IF;
+END $$;
 
 -- Allow locked_by, mapped_by, and validated_by in tasks to be NULL
-ALTER TABLE tasks
-ALTER COLUMN locked_by DROP NOT NULL,
-ALTER COLUMN mapped_by DROP NOT NULL,
-ALTER COLUMN validated_by DROP NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'locked_by'
+        AND is_nullable = 'NO'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN locked_by DROP NOT NULL;
+    END IF;
+
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'mapped_by'
+        AND is_nullable = 'NO'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN mapped_by DROP NOT NULL;
+    END IF;
+
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'validated_by'
+        AND is_nullable = 'NO'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN validated_by DROP NOT NULL;
+    END IF;
+END $$;
 
 -- Commit the transaction
 COMMIT;
diff --git a/src/backend/migrations/revert/009-delete-user.sql b/src/backend/migrations/revert/009-delete-user.sql
index 67bcc5d21..131b6b064 100644
--- a/src/backend/migrations/revert/009-delete-user.sql
+++ b/src/backend/migrations/revert/009-delete-user.sql
@@ -5,21 +5,85 @@
 BEGIN;
 
 -- Disallow user_id in task_history to be NULL
-ALTER TABLE task_history
-ALTER COLUMN user_id SET NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'task_history'
+        AND column_name = 'user_id'
+        AND is_nullable = 'YES'
+    ) THEN
+        ALTER TABLE task_history
+        ALTER COLUMN user_id SET NOT NULL;
+    END IF;
+END $$;
 
 -- Remove the column username from task_history
-ALTER TABLE task_history
-DROP COLUMN username;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'task_history'
+        AND column_name = 'username'
+    ) THEN
+        ALTER TABLE task_history
+        DROP COLUMN username;
+    END IF;
+END $$;
 
 -- Disallow author_id in projects to be NULL
-ALTER TABLE projects ALTER COLUMN author_id SET NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'projects'
+        AND column_name = 'author_id'
+        AND is_nullable = 'YES'
+    ) THEN
+        ALTER TABLE projects
+        ALTER COLUMN author_id SET NOT NULL;
+    END IF;
+END $$;
 
 -- Disallow locked_by, mapped_by, and validated_by in tasks to be NULL
-ALTER TABLE tasks
-ALTER COLUMN locked_by SET NOT NULL,
-ALTER COLUMN mapped_by SET NOT NULL,
-ALTER COLUMN validated_by SET NOT NULL;
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'locked_by'
+        AND is_nullable = 'YES'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN locked_by SET NOT NULL;
+    END IF;
+
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'mapped_by'
+        AND is_nullable = 'YES'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN mapped_by SET NOT NULL;
+    END IF;
+
+    IF EXISTS (
+        SELECT 1
+        FROM information_schema.columns
+        WHERE table_name = 'tasks'
+        AND column_name = 'validated_by'
+        AND is_nullable = 'YES'
+    ) THEN
+        ALTER TABLE tasks
+        ALTER COLUMN validated_by SET NOT NULL;
+    END IF;
+END $$;
 
 -- Commit the transaction
 COMMIT;