diff --git a/src/ethproto/wrappers.py b/src/ethproto/wrappers.py
index 89b9417..97131d3 100644
--- a/src/ethproto/wrappers.py
+++ b/src/ethproto/wrappers.py
@@ -18,6 +18,8 @@
 ETHERSCAN_TOKEN = env.str("ETHERSCAN_TOKEN", None)
 ETHERSCAN_DOMAIN = env.str("ETHERSCAN_DOMAIN", "api.etherscan.io")
 ETHERSCAN_URL = env.str("ETHERSCAN_URL", "https://{domain}/v2/api?apikey={token}&chainid={chainid}&")
+ETHERSCAN_CHAIN_ID = env.int("ETHERSCAN_CHAIN_ID", None)
+
 AMOUNT_DECIMALS = env.int("AMOUNT_DECIMALS", 18)
 AMOUNT_CLASSNAME = env.str("AMOUNT_CLASSNAME", None)
 
@@ -31,6 +33,10 @@
 _providers = {}
 
 
+class EtherscanError(Exception):
+    ...
+
+
 def get_provider(provider_key=None):
     global DEFAULT_PROVIDER
     provider_key = provider_key or DEFAULT_PROVIDER
@@ -266,9 +272,8 @@ def get_events(self, eth_wrapper, event_name, filter_kwargs={}):
     def get_etherscan_url(self):
         if ETHERSCAN_TOKEN is None:
             return None
-        return ETHERSCAN_URL.format(
-            token=ETHERSCAN_TOKEN, domain=ETHERSCAN_DOMAIN, chainid=self.w3.eth.chain_id
-        )
+        chain_id = ETHERSCAN_CHAIN_ID or self.w3.eth.chain_id
+        return ETHERSCAN_URL.format(token=ETHERSCAN_TOKEN, domain=ETHERSCAN_DOMAIN, chainid=chain_id)
 
     def get_first_block(self, eth_wrapper):
         etherscan_url = self.get_etherscan_url()
@@ -283,9 +288,12 @@ def get_first_block(self, eth_wrapper):
         resp = requests.get(url)
         resp.raise_for_status()
         resp = resp.json()
-        if not resp["result"]:
-            return -1
-        return int(resp["result"][0]["blockNumber"])
+        if resp.get("status") != "1":
+            raise EtherscanError(f"Failed to get first block from {etherscan_url}:  {resp}")
+        try:
+            return int(resp["result"][0]["blockNumber"])
+        except (KeyError, TypeError):
+            raise EtherscanError(f"Failed to parse first block for {address}: {resp}")
 
     def get_contract_address(self, eth_wrapper):
         return eth_wrapper.contract.address
diff --git a/tests/test_aa_bundler.py b/tests/test_aa_bundler.py
index 8cd3845..4e53c61 100644
--- a/tests/test_aa_bundler.py
+++ b/tests/test_aa_bundler.py
@@ -5,13 +5,21 @@
 
 import pytest
 from hexbytes import HexBytes
-from web3.auto import w3
+from web3 import HTTPProvider, Web3
 from web3.constants import HASH_ZERO
+from web3.middleware import ExtraDataToPOAMiddleware
 
 from ethproto import aa_bundler
 from ethproto.test_utils import factories
 
 
+@pytest.fixture
+def w3():
+    w3 = Web3(HTTPProvider("http://example.org"))
+    w3.middleware_onion.inject(ExtraDataToPOAMiddleware, layer=0)
+    return w3
+
+
 def test_pack_two():
     assert aa_bundler.pack_two(0, 0) == HASH_ZERO
     assert aa_bundler.pack_two(1, 2) == "0x0000000000000000000000000000000100000000000000000000000000000002"
@@ -166,8 +174,8 @@ def test_get_nonce_with_local_cache(fetch_nonce_mock, randint_mock):
         fetch_nonce_mock.assert_not_called()
 
 
-def test_send_transaction():
-    w3 = MagicMock()
+def test_send_transaction(w3):
+    w3.eth = MagicMock()
     w3.eth.chain_id = CHAIN_ID
 
     tx = aa_bundler.Tx(
@@ -275,7 +283,8 @@ def worker():
 
 
 @pytest.mark.vcr
-def test_build_user_operation():
+def test_build_user_operation(w3):
+
     tx = aa_bundler.Tx(
         value=0,
         chain_id=137,