diff --git a/alembic/versions/114d3a68c1fd_add_updated_on_column_to_issues.py b/alembic/versions/114d3a68c1fd_add_updated_on_column_to_issues.py
index 89cf9a9..051ecf1 100644
--- a/alembic/versions/114d3a68c1fd_add_updated_on_column_to_issues.py
+++ b/alembic/versions/114d3a68c1fd_add_updated_on_column_to_issues.py
@@ -24,6 +24,7 @@ def upgrade():
             default=datetime.datetime.utcnow,
             onupdate=datetime.datetime.utcnow)
     )
+    # Update all the tickets having comments
     op.execute('''
 UPDATE "issues" SET last_updated=o_date
 FROM (
@@ -32,14 +33,21 @@ FROM (
     ORDER BY o_date DESC
 ) AS subq
 WHERE "issues".uid = issue_uid;''')
+    # Update all the tickets without comments
     op.execute('''UPDATE "issues" SET last_updated=date_created '''
                '''WHERE last_updated IS NULL;''')
+    # Require `last_updated` no NULL at the DB level
+    op.alter_column(
+        'issues', 'last_updated',
+        nullable=False, existing_nullable=True)
+
     op.add_column(
         'pull_requests',
         sa.Column('last_updated', sa.DateTime, nullable=True,
             default=datetime.datetime.utcnow,
             onupdate=datetime.datetime.utcnow)
     )
+    # Update all the PRs having comments
     op.execute('''
 UPDATE "pull_requests" SET last_updated=o_date
 FROM (
@@ -48,8 +56,13 @@ FROM (
     ORDER BY o_date DESC
 ) AS subq
 WHERE "pull_requests".uid = pull_request_uid;''')
+    # Update all the PRs without comments
     op.execute('''UPDATE "pull_requests" SET last_updated=date_created '''
                '''WHERE last_updated IS NULL;''')
+    # Require `last_updated` no NULL at the DB level
+    op.alter_column(
+        'pull_requests', 'last_updated',
+        nullable=False, existing_nullable=True)
 
 
 def downgrade():
diff --git a/pagure/lib/model.py b/pagure/lib/model.py
index be14733..db1abd2 100644
--- a/pagure/lib/model.py
+++ b/pagure/lib/model.py
@@ -665,7 +665,7 @@ class Issue(BASE):
     close_status = sa.Column(sa.Text, nullable=True)
     date_created = sa.Column(sa.DateTime, nullable=False,
                              default=datetime.datetime.utcnow)
-    last_updated = sa.Column(sa.DateTime, nullable=True,
+    last_updated = sa.Column(sa.DateTime, nullable=False,
                              default=datetime.datetime.utcnow,
                              onupdate=datetime.datetime.utcnow)
     closed_at = sa.Column(sa.DateTime, nullable=True)
@@ -1120,7 +1120,7 @@ class PullRequest(BASE):
         default=sa.func.now(),
         onupdate=sa.func.now())
 
-    last_updated = sa.Column(sa.DateTime, nullable=True,
+    last_updated = sa.Column(sa.DateTime, nullable=False,
                              default=datetime.datetime.utcnow,
                              onupdate=datetime.datetime.utcnow)