diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetEvmRegistries.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetEvmRegistries.java
index ae8cdd0c7f..3775daf76b 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetEvmRegistries.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetEvmRegistries.java
@@ -12,8 +12,6 @@
  */
 package tech.pegasys.pantheon.ethereum.mainnet;
 
-import static tech.pegasys.pantheon.ethereum.mainnet.MainnetProtocolSpecs.ISTANBUL_ACCOUNT_VERSION;
-
 import tech.pegasys.pantheon.ethereum.core.Account;
 import tech.pegasys.pantheon.ethereum.vm.EVM;
 import tech.pegasys.pantheon.ethereum.vm.GasCalculator;
@@ -135,7 +133,7 @@ static EVM constantinople(final GasCalculator gasCalculator) {
   }
 
   static EVM istanbul(final GasCalculator gasCalculator, final BigInteger chainId) {
-    final OperationRegistry registry = new OperationRegistry(2);
+    final OperationRegistry registry = new OperationRegistry();
 
     registerIstanbulOpcodes(registry, gasCalculator, Account.DEFAULT_VERSION, chainId);
 
@@ -271,14 +269,11 @@ private static void registerIstanbulOpcodes(
     registry.put(
         new SStoreOperation(gasCalculator, SStoreOperation.EIP_1706_MINIMUM),
         Account.DEFAULT_VERSION);
-
-    registerConstantinopleOpcodes(registry, gasCalculator, ISTANBUL_ACCOUNT_VERSION);
     registry.put(
         new ChainIdOperation(gasCalculator, Bytes32.leftPad(BytesValue.of(chainId.toByteArray()))),
-        ISTANBUL_ACCOUNT_VERSION);
-    registerConstantinopleOpcodes(registry, gasCalculator, ISTANBUL_ACCOUNT_VERSION);
+        Account.DEFAULT_VERSION);
     registry.put(
         new SStoreOperation(gasCalculator, SStoreOperation.EIP_1706_MINIMUM),
-        MainnetProtocolSpecs.ISTANBUL_ACCOUNT_VERSION);
+        Account.DEFAULT_VERSION);
   }
 }
diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetPrecompiledContractRegistries.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetPrecompiledContractRegistries.java
index 84245f0d2a..98f3c0e44e 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetPrecompiledContractRegistries.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetPrecompiledContractRegistries.java
@@ -12,8 +12,6 @@
  */
 package tech.pegasys.pantheon.ethereum.mainnet;
 
-import static tech.pegasys.pantheon.ethereum.mainnet.MainnetProtocolSpecs.ISTANBUL_ACCOUNT_VERSION;
-
 import tech.pegasys.pantheon.ethereum.core.Account;
 import tech.pegasys.pantheon.ethereum.core.Address;
 import tech.pegasys.pantheon.ethereum.mainnet.precompiles.AltBN128AddPrecompiledContract;
@@ -87,21 +85,19 @@ public static PrecompileContractRegistry istanbul(
     final PrecompileContractRegistry registry = new PrecompileContractRegistry();
     populateForByzantium(
         registry, precompiledContractConfiguration.getGasCalculator(), Account.DEFAULT_VERSION);
-    populateForByzantium(
-        registry, precompiledContractConfiguration.getGasCalculator(), ISTANBUL_ACCOUNT_VERSION);
     registry.put(
         Address.ALTBN128_ADD,
-        ISTANBUL_ACCOUNT_VERSION,
+        Account.DEFAULT_VERSION,
         AltBN128AddPrecompiledContract.istanbul(
             precompiledContractConfiguration.getGasCalculator()));
     registry.put(
         Address.ALTBN128_MUL,
-        ISTANBUL_ACCOUNT_VERSION,
+        Account.DEFAULT_VERSION,
         AltBN128MulPrecompiledContract.istanbul(
             precompiledContractConfiguration.getGasCalculator()));
     registry.put(
         Address.ALTBN128_PAIRING,
-        ISTANBUL_ACCOUNT_VERSION,
+        Account.DEFAULT_VERSION,
         AltBN128PairingPrecompiledContract.istanbul(
             precompiledContractConfiguration.getGasCalculator()));
 
diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetProtocolSpecs.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetProtocolSpecs.java
index ee83880bdd..48dcb606cc 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetProtocolSpecs.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/mainnet/MainnetProtocolSpecs.java
@@ -51,8 +51,6 @@ public abstract class MainnetProtocolSpecs {
 
   public static final int SPURIOUS_DRAGON_CONTRACT_SIZE_LIMIT = 24576;
 
-  public static final int ISTANBUL_ACCOUNT_VERSION = 1;
-
   private static final Address RIPEMD160_PRECOMPILE =
       Address.fromHexString("0x0000000000000000000000000000000000000003");
 
@@ -293,7 +291,6 @@ public static ProtocolSpecBuilder<Void> istanbulDefinition(
       final boolean enableRevertReason) {
     final int contractSizeLimit =
         configContractSizeLimit.orElse(SPURIOUS_DRAGON_CONTRACT_SIZE_LIMIT);
-    final int stackSizeLimit = configStackSizeLimit.orElse(DEFAULT_MAX_STACK_SIZE);
     return constantinopleFixDefinition(
             chainId, configContractSizeLimit, configStackSizeLimit, enableRevertReason)
         .gasCalculator(IstanbulGasCalculator::new)
@@ -301,34 +298,6 @@ public static ProtocolSpecBuilder<Void> istanbulDefinition(
             gasCalculator ->
                 MainnetEvmRegistries.istanbul(gasCalculator, chainId.orElse(BigInteger.ZERO)))
         .precompileContractRegistryBuilder(MainnetPrecompiledContractRegistries::istanbul)
-        .transactionProcessorBuilder(
-            (gasCalculator,
-                transactionValidator,
-                contractCreationProcessor,
-                messageCallProcessor) ->
-                new MainnetTransactionProcessor(
-                    gasCalculator,
-                    transactionValidator,
-                    contractCreationProcessor,
-                    messageCallProcessor,
-                    true,
-                    stackSizeLimit,
-                    ISTANBUL_ACCOUNT_VERSION))
-        .privateTransactionProcessorBuilder(
-            (gasCalculator,
-                transactionValidator,
-                contractCreationProcessor,
-                messageCallProcessor,
-                privateTransactionValidator) ->
-                new PrivateTransactionProcessor(
-                    gasCalculator,
-                    transactionValidator,
-                    contractCreationProcessor,
-                    messageCallProcessor,
-                    false,
-                    stackSizeLimit,
-                    ISTANBUL_ACCOUNT_VERSION,
-                    privateTransactionValidator))
         .contractCreationProcessorBuilder(
             (gasCalculator, evm) ->
                 new MainnetContractCreationProcessor(
@@ -337,8 +306,7 @@ public static ProtocolSpecBuilder<Void> istanbulDefinition(
                     true,
                     Collections.singletonList(MaxCodeSizeRule.of(contractSizeLimit)),
                     1,
-                    SPURIOUS_DRAGON_FORCE_DELETE_WHEN_EMPTY_ADDRESSES,
-                    ISTANBUL_ACCOUNT_VERSION))
+                    SPURIOUS_DRAGON_FORCE_DELETE_WHEN_EMPTY_ADDRESSES))
         .name("Istanbul");
   }