diff --git a/Sources/XMTPiOS/Client.swift b/Sources/XMTPiOS/Client.swift
index 010602d2..8925e642 100644
--- a/Sources/XMTPiOS/Client.swift
+++ b/Sources/XMTPiOS/Client.swift
@@ -197,8 +197,8 @@ public final class Client {
 	}
 
 	public static func createV3(account: SigningKey, options: ClientOptions) async throws -> Client {
-		let accountAddress = account.isSmartContractWallet ?
-			"eip155:\(String(describing: account.chainId)):\(account.address.lowercased())" :
+		let accountAddress = account.chainId != nil ?
+			"eip155:\(String(describing: account.chainId!)):\(account.address.lowercased())" :
 			account.address
 		let inboxId = try await getOrCreateInboxId(options: options, address: accountAddress)
 
@@ -210,9 +210,9 @@ public final class Client {
 		)
 	}
 	
-	public static func buildV3(address: String, chainId: Int64? = nil, options: ClientOptions) async throws -> Client {
+	public static func buildV3(address: String, chainId: UInt64? = nil, options: ClientOptions) async throws -> Client {
 		let accountAddress = chainId != nil ?
-			"eip155:\(String(describing: chainId)):\(address.lowercased())" :
+			"eip155:\(String(describing: chainId!)):\(address.lowercased())" :
 			address
 		let inboxId = try await getOrCreateInboxId(options: options, address: accountAddress)
 
diff --git a/Sources/XMTPiOS/SigningKey.swift b/Sources/XMTPiOS/SigningKey.swift
index 5c720edf..c9b4971a 100644
--- a/Sources/XMTPiOS/SigningKey.swift
+++ b/Sources/XMTPiOS/SigningKey.swift
@@ -24,10 +24,10 @@ public protocol SigningKey {
 	var isSmartContractWallet: Bool { get }
 	
 	/// The name of the chainId for example "1"
-	var chainId: Int64? { get }
+	var chainId: UInt64? { get }
 	
 	/// The blockNumber of the chain for example "1"
-	var blockNumber: Int64? { get }
+	var blockNumber: UInt64? { get }
 
 	/// Sign the data and return a secp256k1 compact recoverable signature.
 	func sign(_ data: Data) async throws -> Signature
@@ -45,11 +45,11 @@ extension SigningKey {
 		return false
 	}
 	
-	public var chainId: Int64? {
+	public var chainId: UInt64? {
 		return nil
 	}
 	
-	public var blockNumber: Int64? {
+	public var blockNumber: UInt64? {
 		return nil
 	}