diff --git a/safe_transaction_service/account_abstraction/serializers.py b/safe_transaction_service/account_abstraction/serializers.py
index 499f3da73..569ae2128 100644
--- a/safe_transaction_service/account_abstraction/serializers.py
+++ b/safe_transaction_service/account_abstraction/serializers.py
@@ -411,14 +411,14 @@ class UserOperationResponseSerializer(serializers.Serializer):
 
     sender = eth_serializers.EthereumAddressField()
     user_operation_hash = eth_serializers.HexadecimalField(source="hash")
-    nonce = serializers.IntegerField(min_value=0)
+    nonce = serializers.CharField()
     init_code = eth_serializers.HexadecimalField(allow_null=True)
     call_data = eth_serializers.HexadecimalField(allow_null=True)
-    call_gas_limit = serializers.IntegerField(min_value=0)
-    verification_gas_limit = serializers.IntegerField(min_value=0)
-    pre_verification_gas = serializers.IntegerField(min_value=0)
-    max_fee_per_gas = serializers.IntegerField(min_value=0)
-    max_priority_fee_per_gas = serializers.IntegerField(min_value=0)
+    call_gas_limit = serializers.CharField()
+    verification_gas_limit = serializers.CharField()
+    pre_verification_gas = serializers.CharField()
+    max_fee_per_gas = serializers.CharField()
+    max_priority_fee_per_gas = serializers.CharField()
     paymaster = eth_serializers.EthereumAddressField(allow_null=True)
     paymaster_data = eth_serializers.HexadecimalField(allow_null=True)
     signature = eth_serializers.HexadecimalField()
diff --git a/safe_transaction_service/account_abstraction/tests/test_views.py b/safe_transaction_service/account_abstraction/tests/test_views.py
index 1c5b03af9..0052812f8 100644
--- a/safe_transaction_service/account_abstraction/tests/test_views.py
+++ b/safe_transaction_service/account_abstraction/tests/test_views.py
@@ -69,16 +69,22 @@ def test_safe_operation_view(self):
             "safeOperationHash": safe_operation.hash,
             "userOperation": {
                 "sender": safe_operation.user_operation.sender,
-                "nonce": safe_operation.user_operation.nonce,
+                "nonce": str(safe_operation.user_operation.nonce),
                 "userOperationHash": safe_operation.user_operation.hash,
                 "ethereumTxHash": safe_operation.user_operation.ethereum_tx_id,
                 "initCode": "0x",
                 "callData": "0x",
-                "callGasLimit": safe_operation.user_operation.call_gas_limit,
-                "verificationGasLimit": safe_operation.user_operation.verification_gas_limit,
-                "preVerificationGas": safe_operation.user_operation.pre_verification_gas,
-                "maxFeePerGas": safe_operation.user_operation.max_fee_per_gas,
-                "maxPriorityFeePerGas": safe_operation.user_operation.max_priority_fee_per_gas,
+                "callGasLimit": str(safe_operation.user_operation.call_gas_limit),
+                "verificationGasLimit": str(
+                    safe_operation.user_operation.verification_gas_limit
+                ),
+                "preVerificationGas": str(
+                    safe_operation.user_operation.pre_verification_gas
+                ),
+                "maxFeePerGas": str(safe_operation.user_operation.max_fee_per_gas),
+                "maxPriorityFeePerGas": str(
+                    safe_operation.user_operation.max_priority_fee_per_gas
+                ),
                 "paymaster": NULL_ADDRESS,
                 "paymasterData": "0x",
                 "entryPoint": safe_operation.user_operation.entry_point,
@@ -149,16 +155,22 @@ def test_safe_operations_view(self):
             "safeOperationHash": safe_operation.hash,
             "userOperation": {
                 "sender": safe_operation.user_operation.sender,
-                "nonce": safe_operation.user_operation.nonce,
+                "nonce": str(safe_operation.user_operation.nonce),
                 "userOperationHash": safe_operation.user_operation.hash,
                 "ethereumTxHash": safe_operation.user_operation.ethereum_tx_id,
                 "initCode": "0x",
                 "callData": "0x",
-                "callGasLimit": safe_operation.user_operation.call_gas_limit,
-                "verificationGasLimit": safe_operation.user_operation.verification_gas_limit,
-                "preVerificationGas": safe_operation.user_operation.pre_verification_gas,
-                "maxFeePerGas": safe_operation.user_operation.max_fee_per_gas,
-                "maxPriorityFeePerGas": safe_operation.user_operation.max_priority_fee_per_gas,
+                "callGasLimit": str(safe_operation.user_operation.call_gas_limit),
+                "verificationGasLimit": str(
+                    safe_operation.user_operation.verification_gas_limit
+                ),
+                "preVerificationGas": str(
+                    safe_operation.user_operation.pre_verification_gas
+                ),
+                "maxFeePerGas": str(safe_operation.user_operation.max_fee_per_gas),
+                "maxPriorityFeePerGas": str(
+                    safe_operation.user_operation.max_priority_fee_per_gas
+                ),
                 "paymaster": NULL_ADDRESS,
                 "paymasterData": "0x",
                 "signature": "0x" + "0" * 24,
@@ -890,16 +902,22 @@ def test_user_operation_view(self):
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         expected = {
             "sender": safe_operation.user_operation.sender,
-            "nonce": safe_operation.user_operation.nonce,
+            "nonce": str(safe_operation.user_operation.nonce),
             "userOperationHash": safe_operation.user_operation.hash,
             "ethereumTxHash": safe_operation.user_operation.ethereum_tx_id,
             "initCode": "0x",
             "callData": "0x",
-            "callGasLimit": safe_operation.user_operation.call_gas_limit,
-            "verificationGasLimit": safe_operation.user_operation.verification_gas_limit,
-            "preVerificationGas": safe_operation.user_operation.pre_verification_gas,
-            "maxFeePerGas": safe_operation.user_operation.max_fee_per_gas,
-            "maxPriorityFeePerGas": safe_operation.user_operation.max_priority_fee_per_gas,
+            "callGasLimit": str(safe_operation.user_operation.call_gas_limit),
+            "verificationGasLimit": str(
+                safe_operation.user_operation.verification_gas_limit
+            ),
+            "preVerificationGas": str(
+                safe_operation.user_operation.pre_verification_gas
+            ),
+            "maxFeePerGas": str(safe_operation.user_operation.max_fee_per_gas),
+            "maxPriorityFeePerGas": str(
+                safe_operation.user_operation.max_priority_fee_per_gas
+            ),
             "paymaster": NULL_ADDRESS,
             "paymasterData": "0x",
             "signature": "0x" + "0" * 24,
@@ -935,7 +953,8 @@ def test_user_operations_view(self):
             response.json(), {"count": 0, "next": None, "previous": None, "results": []}
         )
         safe_operation = factories.SafeOperationFactory(
-            user_operation__sender=safe_address
+            user_operation__sender=safe_address,
+            user_operation__nonce=131872201376309576872419307987365003264,
         )
         response = self.client.get(
             reverse("v1:account_abstraction:user-operations", args=(safe_address,))
@@ -943,16 +962,22 @@ def test_user_operations_view(self):
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         expected = {
             "sender": safe_operation.user_operation.sender,
-            "nonce": safe_operation.user_operation.nonce,
+            "nonce": str(safe_operation.user_operation.nonce),
             "userOperationHash": safe_operation.user_operation.hash,
             "ethereumTxHash": safe_operation.user_operation.ethereum_tx_id,
             "initCode": "0x",
             "callData": "0x",
-            "callGasLimit": safe_operation.user_operation.call_gas_limit,
-            "verificationGasLimit": safe_operation.user_operation.verification_gas_limit,
-            "preVerificationGas": safe_operation.user_operation.pre_verification_gas,
-            "maxFeePerGas": safe_operation.user_operation.max_fee_per_gas,
-            "maxPriorityFeePerGas": safe_operation.user_operation.max_priority_fee_per_gas,
+            "callGasLimit": str(safe_operation.user_operation.call_gas_limit),
+            "verificationGasLimit": str(
+                safe_operation.user_operation.verification_gas_limit
+            ),
+            "preVerificationGas": str(
+                safe_operation.user_operation.pre_verification_gas
+            ),
+            "maxFeePerGas": str(safe_operation.user_operation.max_fee_per_gas),
+            "maxPriorityFeePerGas": str(
+                safe_operation.user_operation.max_priority_fee_per_gas
+            ),
             "paymaster": NULL_ADDRESS,
             "paymasterData": "0x",
             "signature": "0x" + "0" * 24,
diff --git a/safe_transaction_service/history/serializers.py b/safe_transaction_service/history/serializers.py
index ad8bd4243..f953ded20 100644
--- a/safe_transaction_service/history/serializers.py
+++ b/safe_transaction_service/history/serializers.py
@@ -809,7 +809,7 @@ def get_data_decoded(self, obj: SafeCreationInfo) -> Dict[str, Any]:
 
 class SafeInfoResponseSerializer(serializers.Serializer):
     address = EthereumAddressField()
-    nonce = serializers.IntegerField()
+    nonce = serializers.CharField()
     threshold = serializers.IntegerField()
     owners = serializers.ListField(child=EthereumAddressField())
     master_copy = EthereumAddressField()
diff --git a/safe_transaction_service/history/tests/test_views.py b/safe_transaction_service/history/tests/test_views.py
index aa47418fb..ef0cc3080 100644
--- a/safe_transaction_service/history/tests/test_views.py
+++ b/safe_transaction_service/history/tests/test_views.py
@@ -3379,16 +3379,22 @@ def test_safe_creation_view(self):
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         expected["user_operation"] = {
             "sender": safe_operation.user_operation.sender,
-            "nonce": safe_operation.user_operation.nonce,
+            "nonce": str(safe_operation.user_operation.nonce),
             "user_operation_hash": safe_operation.user_operation.hash,
             "ethereum_tx_hash": internal_tx.ethereum_tx_id,
             "init_code": "0x1234",
             "call_data": "0x",
-            "call_gas_limit": safe_operation.user_operation.call_gas_limit,
-            "verification_gas_limit": safe_operation.user_operation.verification_gas_limit,
-            "pre_verification_gas": safe_operation.user_operation.pre_verification_gas,
-            "max_fee_per_gas": safe_operation.user_operation.max_fee_per_gas,
-            "max_priority_fee_per_gas": safe_operation.user_operation.max_priority_fee_per_gas,
+            "call_gas_limit": str(safe_operation.user_operation.call_gas_limit),
+            "verification_gas_limit": str(
+                safe_operation.user_operation.verification_gas_limit
+            ),
+            "pre_verification_gas": str(
+                safe_operation.user_operation.pre_verification_gas
+            ),
+            "max_fee_per_gas": str(safe_operation.user_operation.max_fee_per_gas),
+            "max_priority_fee_per_gas": str(
+                safe_operation.user_operation.max_priority_fee_per_gas
+            ),
             "paymaster": safe_operation.user_operation.paymaster,
             "paymaster_data": "0x",
             "signature": "0x" + safe_operation.user_operation.signature.hex(),
@@ -3518,7 +3524,7 @@ def test_safe_info_view(self):
             response.data,
             {
                 "address": blockchain_safe.address,
-                "nonce": 0,
+                "nonce": "0",
                 "threshold": blockchain_safe.retrieve_threshold(),
                 "owners": blockchain_safe.retrieve_owners(),
                 "master_copy": blockchain_safe.retrieve_master_copy_address(),