diff --git a/acmsite/auth/__init__.py b/acmsite/auth/__init__.py
index 8c2f816..bffd645 100644
--- a/acmsite/auth/__init__.py
+++ b/acmsite/auth/__init__.py
@@ -27,10 +27,11 @@ def oauth2_callback():
     resp.raise_for_status()
     profile = resp.json()
     print(profile)
-    u = User.query.filter_by(email=profile['mail']).first()
+    u = User.query.filter_by(microsoft_id=profile['id']).first()
     if u is None:
         u = User(
             id=ulid.ulid(),
+            microsoft_id=profile['id'],
             password='',
             email=profile['mail'],
             first_name=profile['givenName'],
diff --git a/acmsite/models.py b/acmsite/models.py
index b3e6244..2539229 100644
--- a/acmsite/models.py
+++ b/acmsite/models.py
@@ -8,6 +8,7 @@ from . import login
 class User(db.Model, UserMixin):
     __tablename__ = "acm_users"
     id = Column(String, primary_key=True)
+    microsoft_id = Column(String, unique=True, nullable=False)
     email = Column(String, unique=True, nullable=True)
     password = Column(String, nullable=False)
     first_name = Column(String, nullable=False)
diff --git a/migrations/versions/300f24071c14_add_microsoft_guid_to_user_model.py b/migrations/versions/300f24071c14_add_microsoft_guid_to_user_model.py
new file mode 100644
index 0000000..3590a29
--- /dev/null
+++ b/migrations/versions/300f24071c14_add_microsoft_guid_to_user_model.py
@@ -0,0 +1,34 @@
+"""add microsoft GUID to user model
+
+Revision ID: 300f24071c14
+Revises: 4fa893cdd432
+Create Date: 2024-04-06 10:15:35.146272
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '300f24071c14'
+down_revision = '4fa893cdd432'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('acm_users', schema=None) as batch_op:
+        batch_op.add_column(sa.Column('microsoft_id', sa.String(), nullable=False))
+        batch_op.create_unique_constraint(None, ['microsoft_id'])
+
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('acm_users', schema=None) as batch_op:
+        batch_op.drop_constraint(None, type_='unique')
+        batch_op.drop_column('microsoft_id')
+
+    # ### end Alembic commands ###