diff --git a/app/models.py b/app/models.py
index e3242445..b5b8a28e 100644
--- a/app/models.py
+++ b/app/models.py
@@ -876,7 +876,7 @@ class PostReplyVote(db.Model):
 class ActivityPubLog(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     direction = db.Column(db.String(3))         # 'in' or 'out'
-    activity_id = db.Column(db.String(100), index=True)
+    activity_id = db.Column(db.String(256), index=True)
     activity_type = db.Column(db.String(50))    # e.g. 'Follow', 'Accept', 'Like', etc
     activity_json = db.Column(db.Text)          # the full json of the activity
     result = db.Column(db.String(10))           # 'success' or 'failure'
diff --git a/app/utils.py b/app/utils.py
index 94b97d43..9ca9414b 100644
--- a/app/utils.py
+++ b/app/utils.py
@@ -609,6 +609,10 @@ def _confidence(ups, downs):
 
 
 def confidence(ups, downs) -> float:
+    if ups is None:
+        ups = 0
+    if downs is None:
+        downs = 0
     if ups + downs == 0:
         return 0.0
     else:
diff --git a/migrations/versions/6b4774eb6349_increase_activity_id_length.py b/migrations/versions/6b4774eb6349_increase_activity_id_length.py
new file mode 100644
index 00000000..b3ba543d
--- /dev/null
+++ b/migrations/versions/6b4774eb6349_increase_activity_id_length.py
@@ -0,0 +1,38 @@
+"""increase activity id length
+
+Revision ID: 6b4774eb6349
+Revises: b86c49cbd9a0
+Create Date: 2024-01-19 07:45:25.845475
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '6b4774eb6349'
+down_revision = 'b86c49cbd9a0'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('activity_pub_log', schema=None) as batch_op:
+        batch_op.alter_column('activity_id',
+               existing_type=sa.VARCHAR(length=100),
+               type_=sa.String(length=256),
+               existing_nullable=True)
+
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('activity_pub_log', schema=None) as batch_op:
+        batch_op.alter_column('activity_id',
+               existing_type=sa.String(length=256),
+               type_=sa.VARCHAR(length=100),
+               existing_nullable=True)
+
+    # ### end Alembic commands ###