diff --git a/siwe_auth/backend.py b/siwe_auth/backend.py
index 3147f31..1a76968 100644
--- a/siwe_auth/backend.py
+++ b/siwe_auth/backend.py
@@ -115,7 +115,7 @@ def authenticate(self, request, signature: str = None, siwe_message: SiweMessage
                     logging.info(f"Created group '{custom_group[0]}'.")
                 group_manager: GroupManager = custom_group[1]
                 if group_manager.is_member(
-                    ethereum_address=wallet.ethereum_address,
+                    wallet=wallet,
                     provider=HTTPProvider(settings.PROVIDER),
                 ):
                     logging.info(
diff --git a/siwe_auth/custom_groups/erc1155.py b/siwe_auth/custom_groups/erc1155.py
index 7388a6e..01945e8 100644
--- a/siwe_auth/custom_groups/erc1155.py
+++ b/siwe_auth/custom_groups/erc1155.py
@@ -54,20 +54,22 @@ def _is_member(
         return expression(balance)
 
     @abstractmethod
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: object, provider: HTTPProvider) -> bool:
         pass
 
 
 class ERC1155OwnerManager(ERC1155Manager):
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: object, provider: HTTPProvider) -> bool:
+        if not self._valid_wallet(wallet=wallet):
+            return False
         try:
             return self._is_member(
-                ethereum_address=ethereum_address,
+                ethereum_address=wallet.ethereum_address,
                 provider=provider,
                 expression=lambda x: x > 0,
             )
         except ValueError:
             logging.error(
-                f"Unable to verify membership of invalid address: {ethereum_address}"
+                f"Unable to verify membership of invalid address: {wallet.ethereum_address}"
             )
         return False
diff --git a/siwe_auth/custom_groups/erc20.py b/siwe_auth/custom_groups/erc20.py
index e00b1ad..a3cb0a1 100644
--- a/siwe_auth/custom_groups/erc20.py
+++ b/siwe_auth/custom_groups/erc20.py
@@ -3,6 +3,7 @@
 from typing import Callable
 
 from siwe_auth.custom_groups.group_manager import GroupManager
+from siwe_auth.utils.data_classes import EthereumBaseClass
 
 from web3 import Web3, HTTPProvider
 
@@ -41,20 +42,22 @@ def _is_member(
         return expression(balance)
 
     @abstractmethod
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: EthereumBaseClass, provider: HTTPProvider) -> bool:
         pass
 
 
 class ERC20OwnerManager(ERC20Manager):
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: EthereumBaseClass, provider: HTTPProvider) -> bool:
+        if not self._valid_wallet(wallet=wallet):
+            return False
         try:
             return self._is_member(
-                ethereum_address=ethereum_address,
+                ethereum_address=wallet.ethereum_address,
                 provider=provider,
                 expression=lambda x: x > 0,
             )
         except ValueError:
             logging.error(
-                f"Unable to verify membership of invalid address: {ethereum_address}"
+                f"Unable to verify membership of invalid address: {wallet.ethereum_address}"
             )
         return False
diff --git a/siwe_auth/custom_groups/erc721.py b/siwe_auth/custom_groups/erc721.py
index 4790395..8f1e974 100644
--- a/siwe_auth/custom_groups/erc721.py
+++ b/siwe_auth/custom_groups/erc721.py
@@ -41,20 +41,22 @@ def _is_member(
         return expression(balance)
 
     @abstractmethod
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: object, provider: HTTPProvider) -> bool:
         pass
 
 
 class ERC721OwnerManager(ERC721Manager):
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: object, provider: HTTPProvider) -> bool:
+        if not self._valid_wallet(wallet=wallet):
+            return False
         try:
             return self._is_member(
-                ethereum_address=ethereum_address,
+                ethereum_address=wallet.ethereum_address,
                 provider=provider,
                 expression=lambda x: x > 0,
             )
         except ValueError:
             logging.error(
-                f"Unable to verify membership of invalid address: {ethereum_address}"
+                f"Unable to verify membership of invalid address: {wallet.ethereum_address}"
             )
         return False
diff --git a/siwe_auth/custom_groups/group_manager.py b/siwe_auth/custom_groups/group_manager.py
index 4166529..dc12b00 100644
--- a/siwe_auth/custom_groups/group_manager.py
+++ b/siwe_auth/custom_groups/group_manager.py
@@ -12,11 +12,14 @@ def __init__(self, config: dict):
         pass
 
     @abstractmethod
-    def is_member(self, ethereum_address: str, provider: HTTPProvider) -> bool:
+    def is_member(self, wallet: object, provider: HTTPProvider) -> bool:
         """
         Membership function to identify if a given ethereum address is part of this class' group.
         :param provider: Web3 provider to use for membership check.
-        :param ethereum_address: Address to check membership of.
+        :param wallet: Object with ethereum_address attribute to check membership of.
         :return: True if address is a member else False
         """
         pass
+
+    def _valid_wallet(self, wallet: object):
+        return wallet.__getattribute__('ethereum_address') is not None
diff --git a/siwe_auth/models.py b/siwe_auth/models.py
index b05721f..199b782 100644
--- a/siwe_auth/models.py
+++ b/siwe_auth/models.py
@@ -1,7 +1,5 @@
 from datetime import datetime
-
 from django.db import models
-
 from django.contrib.auth.models import (
     BaseUserManager,
     AbstractBaseUser,