diff --git a/.github/workflows/lint.backend.yml b/.github/workflows/lint.backend.yml
index e5514ae4..8aae8ed9 100644
--- a/.github/workflows/lint.backend.yml
+++ b/.github/workflows/lint.backend.yml
@@ -19,9 +19,9 @@ jobs:
       - name: Install test requirements
         working-directory: ./backend
         run: pip install -r requirements.txt
-      # - name: Mypy type check
-      #   working-directory: ./backend
-      #   run: mypy moonstream/
+      - name: Mypy type check
+        working-directory: ./backend
+        run: mypy moonstream/
       - name: Black syntax check
         working-directory: ./backend
         run: black --check moonstream/
diff --git a/backend/moonstream/actions.py b/backend/moonstream/actions.py
index eed979a9..87a2dce6 100644
--- a/backend/moonstream/actions.py
+++ b/backend/moonstream/actions.py
@@ -1,14 +1,11 @@
-from datetime import datetime
+import json
 import logging
+from typing import Dict, Any, List, Optional
 
-
-from typing import Dict, Any, List, Optional, Union
-
-from sqlalchemy.engine.base import Transaction
+import boto3  # type: ignore
 from moonstreamdb.models import (
     EthereumBlock,
     EthereumTransaction,
-    EthereumPendingTransaction,
     EthereumAddress,
     EthereumLabel,
 )
@@ -16,10 +13,7 @@ from sqlalchemy import or_, and_, text
 from sqlalchemy.orm import Session
 
 from . import data
-
 from .settings import DEFAULT_STREAM_TIMEINTERVAL, ETHERSCAN_SMARTCONTRACTS_BUCKET
-import boto3
-import json
 
 logger = logging.getLogger(__name__)
 
@@ -299,8 +293,8 @@ def get_source_code(
 
 
 def get_address_labels(
-    db_session: Session, start: int, limit: int, addresses: Optional[List[str]] = None
-) -> List[EthereumAddress]:
+    db_session: Session, start: int, limit: int, addresses: Optional[str] = None
+) -> data.AddressListLabelsResponse:
     """
     Attach labels to addresses.
     """
diff --git a/backend/moonstream/routes/txinfo.py b/backend/moonstream/routes/txinfo.py
index ee0716a9..2e980425 100644
--- a/backend/moonstream/routes/txinfo.py
+++ b/backend/moonstream/routes/txinfo.py
@@ -97,8 +97,8 @@ async def txinfo_ethereum_blockchain_handler(
 )
 async def addresses_labels_handler(
     addresses: Optional[str] = Query(None),
-    start: Optional[int] = Query(0),
-    limit: Optional[int] = Query(100),
+    start: int = Query(0),
+    limit: int = Query(100),
     db_session: Session = Depends(yield_db_session),
 ) -> data.AddressListLabelsResponse:
     """
@@ -110,11 +110,11 @@ async def addresses_labels_handler(
             status_code=406, detail="The limit cannot exceed 100 addresses"
         )
     try:
-        addresses = actions.get_address_labels(
+        addresses_response = actions.get_address_labels(
             db_session=db_session, start=start, limit=limit, addresses=addresses
         )
     except Exception as err:
         logger.error(f"Unable to get info about Ethereum addresses {err}")
         raise HTTPException(status_code=500)
 
-    return addresses
+    return addresses_response
diff --git a/backend/moonstream/settings.py b/backend/moonstream/settings.py
index 440176f6..4b31e73c 100644
--- a/backend/moonstream/settings.py
+++ b/backend/moonstream/settings.py
@@ -16,8 +16,8 @@ MOONSTREAM_DATA_JOURNAL_ID = os.environ.get("MOONSTREAM_DATA_JOURNAL_ID")
 if MOONSTREAM_DATA_JOURNAL_ID is None:
     raise ValueError("MOONSTREAM_DATA_JOURNAL_ID environment variable must be set")
 
-MOONSTREAM_ADMIN_ACCESS_TOKEN = os.environ.get("MOONSTREAM_ADMIN_ACCESS_TOKEN")
-if MOONSTREAM_ADMIN_ACCESS_TOKEN is None:
+MOONSTREAM_ADMIN_ACCESS_TOKEN = os.environ.get("MOONSTREAM_ADMIN_ACCESS_TOKEN", "")
+if MOONSTREAM_ADMIN_ACCESS_TOKEN == "":
     raise ValueError("MOONSTREAM_ADMIN_ACCESS_TOKEN environment variable must be set")
 
 # Origin