diff --git a/Postbox/AccountManagerAtomicState.swift b/Postbox/AccountManagerAtomicState.swift
index c1ccf1d038..4af41ff6d9 100644
--- a/Postbox/AccountManagerAtomicState.swift
+++ b/Postbox/AccountManagerAtomicState.swift
@@ -1,6 +1,6 @@
 import Foundation
 
-struct AccountManagerAtomicState: Codable {
+final class AccountManagerAtomicState: Codable {
     var records: [AccountRecordId: AccountRecord]
     var currentRecordId: AccountRecordId?
     var currentAuthRecord: AuthAccountRecord?
diff --git a/Postbox/AccountRecord.swift b/Postbox/AccountRecord.swift
index 3589f826c2..9b8f2c5681 100644
--- a/Postbox/AccountRecord.swift
+++ b/Postbox/AccountRecord.swift
@@ -1,6 +1,6 @@
 import Foundation
 
-public protocol AccountRecordAttribute: PostboxCoding {
+public protocol AccountRecordAttribute: class, PostboxCoding {
     func isEqual(to: AccountRecordAttribute) -> Bool
 }
 
@@ -34,7 +34,7 @@ public func generateAccountRecordId() -> AccountRecordId {
     return AccountRecordId(rawValue: id)
 }
 
-public struct AccountRecord: PostboxCoding, Equatable, Codable {
+public final class AccountRecord: PostboxCoding, Equatable, Codable {
     enum CodingKeys: String, CodingKey {
         case id
         case attributes
diff --git a/Postbox/MessageHistoryTable.swift b/Postbox/MessageHistoryTable.swift
index 101ae0c548..5c9e1dcb0c 100644
--- a/Postbox/MessageHistoryTable.swift
+++ b/Postbox/MessageHistoryTable.swift
@@ -873,7 +873,9 @@ final class MessageHistoryTable: Table {
         if let lower = lower, let upper = upper, let groupInfo = lower.groupInfo, lower.groupingKey == upper.groupingKey {
             assert(upper.groupInfo != nil)
             if lower.groupInfo != upper.groupInfo {
-                self.updateSameGroupInfosInNamespace(lowerBound: index, from: upper.groupInfo!, to: groupInfo, updatedGroupInfos: &updatedGroupInfos)
+                if let upperGroupInfo = upper.groupInfo {
+                    self.updateSameGroupInfosInNamespace(lowerBound: index, from: groupInfo, to: upperGroupInfo, updatedGroupInfos: &updatedGroupInfos)
+                }
             }
         }
     }
diff --git a/Postbox/SqliteValueBox.swift b/Postbox/SqliteValueBox.swift
index 01e08b0120..a6f77db04f 100644
--- a/Postbox/SqliteValueBox.swift
+++ b/Postbox/SqliteValueBox.swift
@@ -442,7 +442,7 @@ public final class SqliteValueBox: ValueBox {
     private func beginInternal(database: Database) {
         precondition(self.queue.isCurrent())
         let resultCode = database.execute("BEGIN IMMEDIATE")
-        precondition(resultCode)
+        assert(resultCode)
     }
     
     private func commitInternal(database: Database) {