diff --git a/alembic/versions/2023_03_19_1509-caf39c6e55fc_in_out_models.py b/alembic/versions/2023_03_19_1509-caf39c6e55fc_in_out_models.py
index fc759e4..e526d36 100644
--- a/alembic/versions/2023_03_19_1509-caf39c6e55fc_in_out_models.py
+++ b/alembic/versions/2023_03_19_1509-caf39c6e55fc_in_out_models.py
@@ -33,9 +33,11 @@ def upgrade() -> None:
     sa.Column('ap_object', sa.JSON(), nullable=False),
     sa.Column('activity_object_ap_id', sa.String(), nullable=True),
     sa.Column('visibility', sa.Enum('PUBLIC', 'UNLISTED', 'FOLLOWERS_ONLY', 'DIRECT', name='visibilityenum'), nullable=False),
+    sa.Column('undo_id', sa.Integer(), nullable=False),
     sa.Column('relates_to_inbox_object_id', sa.Integer(), nullable=True),
     sa.Column('relates_to_outbox_object_id', sa.Integer(), nullable=True),
     sa.ForeignKeyConstraint(['actor_id'], ['actor.id'], ),
+    sa.ForeignKeyConstraint(['undo_id'], ['inbox.id'], ),
     sa.ForeignKeyConstraint(['relates_to_inbox_object_id'], ['inbox.id'], ),
     sa.ForeignKeyConstraint(['relates_to_outbox_object_id'], ['outbox.id'], ),
     sa.PrimaryKeyConstraint('id')
diff --git a/app/models.py b/app/models.py
index 3b8029f..1d53035 100644
--- a/app/models.py
+++ b/app/models.py
@@ -65,6 +65,7 @@ class InboxObject(Base):
 
     visibility = Column(Enum(ap.VisibilityEnum), nullable=False)
 
+    undo_id = Column(Integer, ForeignKey("inbox.id"), nullable=True)
     relates_to_inbox_object_id = Column(
         Integer,
         ForeignKey("inbox.id"),