diff --git a/src/core/AutoTypeAssociations.cpp b/src/core/AutoTypeAssociations.cpp
index 5ec4eb3b3..04221733f 100644
--- a/src/core/AutoTypeAssociations.cpp
+++ b/src/core/AutoTypeAssociations.cpp
@@ -103,6 +103,15 @@ int AutoTypeAssociations::size() const
     return m_associations.size();
 }
 
+int AutoTypeAssociations::associationsSize() const
+{
+    int size = 0;
+    for (const Association &association : m_associations) {
+        size += association.sequence.toUtf8().size() + association.window.toUtf8().size();
+    }
+    return size;
+}
+
 void AutoTypeAssociations::clear()
 {
     m_associations.clear();
diff --git a/src/core/AutoTypeAssociations.h b/src/core/AutoTypeAssociations.h
index 61ef3fd4a..31e58cda0 100644
--- a/src/core/AutoTypeAssociations.h
+++ b/src/core/AutoTypeAssociations.h
@@ -43,6 +43,7 @@ public:
     AutoTypeAssociations::Association get(int index) const;
     QList<AutoTypeAssociations::Association> getAll() const;
     int size() const;
+    int associationsSize() const;
     void clear();
 
 private:
diff --git a/src/core/Entry.cpp b/src/core/Entry.cpp
index ed8860835..2f4105fc6 100644
--- a/src/core/Entry.cpp
+++ b/src/core/Entry.cpp
@@ -582,22 +582,24 @@ void Entry::truncateHistory()
     int histMaxSize = db->metadata()->historyMaxSize();
     if (histMaxSize > -1) {
         int size = 0;
-        QSet<QByteArray> foundAttachments = attachments()->values().toSet();
+        QSet<QByteArray> foundAttachments = attachments()->values();
 
         QMutableListIterator<Entry*> i(m_history);
         i.toBack();
+        const QRegularExpression delimiter(",|:|;");
         while (i.hasPrevious()) {
             Entry* historyItem = i.previous();
 
             // don't calculate size if it's already above the maximum
             if (size <= histMaxSize) {
                 size += historyItem->attributes()->attributesSize();
-
-                const QSet<QByteArray> newAttachments = historyItem->attachments()->values().toSet() - foundAttachments;
-                for (const QByteArray& attachment : newAttachments) {
-                    size += attachment.size();
+                size += historyItem->autoTypeAssociations()->associationsSize();
+                size += historyItem->attachments()->attachmentsSize();
+                const QStringList tags = historyItem->tags().split(delimiter, QString::SkipEmptyParts);
+                for (const QString& tag : tags) {
+                    size += tag.toUtf8().size();
                 }
-                foundAttachments += newAttachments;
+                foundAttachments += historyItem->attachments()->values();
             }
 
             if (size > histMaxSize) {
@@ -633,7 +635,7 @@ Entry* Entry::clone(CloneFlags flags) const
         entry->m_attributes->set(EntryAttributes::PasswordKey, password.toUpper(), m_attributes->isProtected(EntryAttributes::PasswordKey));
     }
 
-    entry->m_autoTypeAssociations->copyDataFrom(this->m_autoTypeAssociations);
+    entry->m_autoTypeAssociations->copyDataFrom(m_autoTypeAssociations);
     if (flags & CloneIncludeHistory) {
         for (Entry* historyItem : m_history) {
             Entry* historyItemClone = historyItem->clone(flags & ~CloneIncludeHistory & ~CloneNewUuid);
@@ -679,6 +681,7 @@ void Entry::beginUpdate()
     m_tmpHistoryItem->m_data = m_data;
     m_tmpHistoryItem->m_attributes->copyDataFrom(m_attributes);
     m_tmpHistoryItem->m_attachments->copyDataFrom(m_attachments);
+    m_tmpHistoryItem->m_autoTypeAssociations->copyDataFrom(m_autoTypeAssociations);
 
     m_modifiedSinceBegin = false;
 }
diff --git a/src/core/EntryAttachments.cpp b/src/core/EntryAttachments.cpp
index 957558609..4dcc0262b 100644
--- a/src/core/EntryAttachments.cpp
+++ b/src/core/EntryAttachments.cpp
@@ -18,6 +18,7 @@
 #include "EntryAttachments.h"
 
 #include <QStringList>
+#include <QSet>
 
 EntryAttachments::EntryAttachments(QObject* parent)
     : QObject(parent)
@@ -34,9 +35,9 @@ bool EntryAttachments::hasKey(const QString& key) const
     return m_attachments.contains(key);
 }
 
-QList<QByteArray> EntryAttachments::values() const
+QSet<QByteArray> EntryAttachments::values() const
 {
-    return m_attachments.values();
+    return m_attachments.values().toSet();
 }
 
 QByteArray EntryAttachments::value(const QString& key) const
@@ -151,3 +152,12 @@ bool EntryAttachments::operator!=(const EntryAttachments& other) const
 {
     return m_attachments != other.m_attachments;
 }
+
+int EntryAttachments::attachmentsSize() const
+{
+    int size = 0;
+    for (auto it = m_attachments.constBegin(); it != m_attachments.constEnd(); ++it) {
+        size += it.key().toUtf8().size() + it.value().size();
+    }
+    return size;
+}
diff --git a/src/core/EntryAttachments.h b/src/core/EntryAttachments.h
index 0dba9543f..c2fa55b44 100644
--- a/src/core/EntryAttachments.h
+++ b/src/core/EntryAttachments.h
@@ -31,7 +31,7 @@ public:
     explicit EntryAttachments(QObject* parent = nullptr);
     QList<QString> keys() const;
     bool hasKey(const QString& key) const;
-    QList<QByteArray> values() const;
+    QSet<QByteArray> values() const;
     QByteArray value(const QString& key) const;
     void set(const QString& key, const QByteArray& value);
     void remove(const QString& key);
@@ -41,6 +41,7 @@ public:
     void copyDataFrom(const EntryAttachments* other);
     bool operator==(const EntryAttachments& other) const;
     bool operator!=(const EntryAttachments& other) const;
+    int attachmentsSize() const;
 
 signals:
     void modified();
diff --git a/src/core/EntryAttributes.cpp b/src/core/EntryAttributes.cpp
index 8cc7f2f0a..629d8e802 100644
--- a/src/core/EntryAttributes.cpp
+++ b/src/core/EntryAttributes.cpp
@@ -283,14 +283,11 @@ void EntryAttributes::clear()
     emit modified();
 }
 
-int EntryAttributes::attributesSize()
+int EntryAttributes::attributesSize() const
 {
     int size = 0;
-
-    QMapIterator<QString, QString> i(m_attributes);
-    while (i.hasNext()) {
-        i.next();
-        size += i.value().toUtf8().size();
+    for (auto it = m_attributes.constBegin(); it != m_attributes.constEnd(); ++it) {
+        size += it.key().toUtf8().size() + it.value().toUtf8().size();
     }
     return size;
 }
diff --git a/src/core/EntryAttributes.h b/src/core/EntryAttributes.h
index f483b8a9b..3eca9171c 100644
--- a/src/core/EntryAttributes.h
+++ b/src/core/EntryAttributes.h
@@ -45,7 +45,7 @@ public:
     void copyCustomKeysFrom(const EntryAttributes* other);
     bool areCustomKeysDifferent(const EntryAttributes* other);
     void clear();
-    int attributesSize();
+    int attributesSize() const;
     void copyDataFrom(const EntryAttributes* other);
     bool operator==(const EntryAttributes& other) const;
     bool operator!=(const EntryAttributes& other) const;
diff --git a/tests/TestEntry.cpp b/tests/TestEntry.cpp
index 47082d12f..598ad33fd 100644
--- a/tests/TestEntry.cpp
+++ b/tests/TestEntry.cpp
@@ -20,7 +20,6 @@
 
 #include <QTest>
 
-#include "core/Database.h"
 #include "core/Entry.h"
 #include "core/Group.h"
 #include "crypto/Crypto.h"
@@ -48,6 +47,7 @@ void TestEntry::testHistoryItemDeletion()
 
     delete entry;
 }
+
 void TestEntry::testCopyDataFrom()
 {
     Entry* entry = new Entry();
diff --git a/tests/TestModified.cpp b/tests/TestModified.cpp
index 70a4a4844..6bc447270 100644
--- a/tests/TestModified.cpp
+++ b/tests/TestModified.cpp
@@ -288,14 +288,14 @@ void TestModified::testEntrySets()
     delete db;
 }
 
-void TestModified::testHistoryItem()
+void TestModified::testHistoryItems()
 {
-    Entry* entry = new Entry();
+    QScopedPointer<Entry> entry(new Entry());
     QDateTime created = entry->timeInfo().creationTime();
     entry->setUuid(Uuid::random());
     entry->setTitle("a");
     entry->setTags("a");
-    EntryAttributes* attributes = new EntryAttributes();
+    QScopedPointer<EntryAttributes> attributes(new EntryAttributes());
     attributes->copyCustomKeysFrom(entry->attributes());
 
     Entry* historyEntry;
@@ -338,15 +338,12 @@ void TestModified::testHistoryItem()
 
     attributes->set("k", "myvalue");
     entry->beginUpdate();
-    entry->attributes()->copyCustomKeysFrom(attributes);
+    entry->attributes()->copyCustomKeysFrom(attributes.data());
     entry->endUpdate();
     QCOMPARE(entry->historyItems().size(), ++historyItemsSize);
     QVERIFY(!entry->historyItems().at(historyItemsSize - 1)->attributes()->keys().contains("k"));
 
-    delete attributes;
-    delete entry;
-
-    Database* db = new Database();
+    QScopedPointer<Database> db(new Database());
     Group* root = db->rootGroup();
     db->metadata()->setHistoryMaxItems(3);
     db->metadata()->setHistoryMaxSize(-1);
@@ -400,12 +397,16 @@ void TestModified::testHistoryItem()
     entry2->endUpdate();
     QCOMPARE(entry2->historyItems().size(), 0);
 
-    db->metadata()->setHistoryMaxItems(-1);
-    db->metadata()->setHistoryMaxSize(17000);
+    const int historyMaxSize = 19000;
 
+    db->metadata()->setHistoryMaxItems(-1);
+    db->metadata()->setHistoryMaxSize(historyMaxSize);
+
+    const QString key("test");
     entry2->beginUpdate();
-    entry2->attachments()->set("test", QByteArray(18000, 'X'));
+    entry2->attachments()->set(key, QByteArray(18000, 'X'));
     entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 18000 + key.size());
     QCOMPARE(entry2->historyItems().size(), 1);
 
     historyEntry2 = entry2->historyItems().at(0);
@@ -417,53 +418,167 @@ void TestModified::testHistoryItem()
     QCOMPARE(entry2->historyItems().size(), 2);
 
     entry2->beginUpdate();
-    entry2->attachments()->remove("test");
+    entry2->attachments()->remove(key);
     entry2->endUpdate();
-    QCOMPARE(entry2->historyItems().size(), 0);
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 0);
+    QCOMPARE(entry2->historyItems().size(), 1);
 
     entry2->beginUpdate();
     entry2->attachments()->set("test2", QByteArray(6000, 'a'));
     entry2->endUpdate();
-    QCOMPARE(entry2->historyItems().size(), 1);
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 6000 + key.size() + 1);
+    QCOMPARE(entry2->historyItems().size(), 2);
 
     entry2->beginUpdate();
     entry2->attachments()->set("test3", QByteArray(6000, 'b'));
     entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 12000 + (key.size() + 1) * 2);
     QCOMPARE(entry2->historyItems().size(), 2);
 
     entry2->beginUpdate();
     entry2->attachments()->set("test4", QByteArray(6000, 'c'));
     entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 18000 + (key.size() + 1) * 3);
     QCOMPARE(entry2->historyItems().size(), 3);
 
     entry2->beginUpdate();
     entry2->attachments()->set("test5", QByteArray(6000, 'd'));
     entry2->endUpdate();
-    QCOMPARE(entry2->historyItems().size(), 4);
-
-    Entry* entry3 = new Entry();
-    entry3->setGroup(root);
-    QCOMPARE(entry3->historyItems().size(), 0);
-
-    entry3->beginUpdate();
-    entry3->attachments()->set("test", QByteArray(6000, 'a'));
-    entry3->endUpdate();
-    QCOMPARE(entry3->historyItems().size(), 1);
-
-    entry3->beginUpdate();
-    entry3->attachments()->set("test", QByteArray(6000, 'b'));
-    entry3->endUpdate();
-    QCOMPARE(entry3->historyItems().size(), 2);
-
-    entry3->beginUpdate();
-    entry3->attachments()->set("test", QByteArray(6000, 'c'));
-    entry3->endUpdate();
-    QCOMPARE(entry3->historyItems().size(), 3);
-
-    entry3->beginUpdate();
-    entry3->attachments()->set("test", QByteArray(6000, 'd'));
-    entry3->endUpdate();
-    QCOMPARE(entry3->historyItems().size(), 2);
-
-    delete db;
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 24000 + (key.size() + 1) * 4);
+    QCOMPARE(entry2->historyItems().size(), 1);
+}
+
+void TestModified::testHistoryMaxSize()
+{
+    QScopedPointer<Database> db(new Database());
+    const QString key("test");
+
+
+    auto entry1 = new Entry();
+    entry1->setGroup(db->rootGroup());
+    QCOMPARE(entry1->historyItems().size(), 0);
+
+    const int reservedSize1 = entry1->attributes()->attributesSize();
+    db->metadata()->setHistoryMaxItems(-1);
+    db->metadata()->setHistoryMaxSize(18000 + key.size() * 3 + reservedSize1 * 4);
+
+    entry1->beginUpdate();
+    entry1->attachments()->set(key, QByteArray(6000, 'a'));
+    entry1->endUpdate();
+    QCOMPARE(entry1->attachments()->attachmentsSize(), 6000 + key.size());
+    QCOMPARE(entry1->historyItems().size(), 1);
+
+    entry1->beginUpdate();
+    entry1->attachments()->set(key, QByteArray(6000, 'b'));
+    entry1->endUpdate();
+    QCOMPARE(entry1->attachments()->attachmentsSize(), 6000 + key.size());
+    QCOMPARE(entry1->historyItems().size(), 2);
+
+    entry1->beginUpdate();
+    entry1->attachments()->set(key, QByteArray(6000, 'c'));
+    entry1->endUpdate();
+    QCOMPARE(entry1->attachments()->attachmentsSize(), 6000 + key.size());
+    QCOMPARE(entry1->historyItems().size(), 3);
+
+    entry1->beginUpdate();
+    entry1->attachments()->set(key, QByteArray(6000, 'd'));
+    entry1->endUpdate();
+    QCOMPARE(entry1->attachments()->attachmentsSize(), 6000 + key.size());
+    QCOMPARE(entry1->historyItems().size(), 4);
+
+
+    auto entry2 = new Entry();
+    entry2->setGroup(db->rootGroup());
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    const int historyMaxSize = 17000;
+    const int reservedSize2 = entry2->attributes()->attributesSize();
+    db->metadata()->setHistoryMaxSize(historyMaxSize);
+
+    entry2->beginUpdate();
+    entry2->attachments()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'a'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), historyMaxSize - reservedSize2 + 1);
+    QCOMPARE(entry2->historyItems().size(), 1);
+
+    // history size overflow
+    entry2->beginUpdate();
+    entry2->attachments()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'b'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->attachments()->remove(key);
+    entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 0);
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->attachments()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'a'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), historyMaxSize - reservedSize2 + 1);
+    QCOMPARE(entry2->historyItems().size(), 1);
+
+    // history size overflow
+    entry2->beginUpdate();
+    entry2->attachments()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'b'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->attachments()->remove(key);
+    entry2->endUpdate();
+    QCOMPARE(entry2->attachments()->attachmentsSize(), 0);
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->setTags(QByteArray(historyMaxSize - reservedSize2 + 1, 'a'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->tags().size(), historyMaxSize - reservedSize2 + 1);
+    QCOMPARE(entry2->historyItems().size(), 1);
+
+    // history size overflow
+    entry2->beginUpdate();
+    entry2->setTags(QByteArray(historyMaxSize - reservedSize2 + 1, 'b'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->setTags("");
+    entry2->endUpdate();
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->attributes()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'a'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->attributes()->attributesSize(), historyMaxSize + 1);
+    QCOMPARE(entry2->historyItems().size(), 1);
+
+    // history size overflow
+    entry2->beginUpdate();
+    entry2->attributes()->set(key, QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'b'));
+    entry2->endUpdate();
+    QCOMPARE(entry2->attributes()->attributesSize(), historyMaxSize + 1);
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    entry2->attributes()->remove(key);
+    entry2->endUpdate();
+    QCOMPARE(entry2->attributes()->attributesSize(), reservedSize2);
+    QCOMPARE(entry2->historyItems().size(), 0);
+
+    entry2->beginUpdate();
+    AutoTypeAssociations::Association association;
+    association.window = key;
+    association.sequence = QByteArray(historyMaxSize - key.size() - reservedSize2 + 1, 'a');
+    entry2->autoTypeAssociations()->add(association);
+    entry2->endUpdate();
+    QCOMPARE(entry2->autoTypeAssociations()->associationsSize(), historyMaxSize - reservedSize2 + 1);
+    QCOMPARE(entry2->historyItems().size(), 1);
+
+    entry2->beginUpdate();
+    entry2->autoTypeAssociations()->remove(0);
+    entry2->endUpdate();
+    QCOMPARE(entry2->autoTypeAssociations()->associationsSize(), 0);
+    QCOMPARE(entry2->historyItems().size(), 0);
 }
diff --git a/tests/TestModified.h b/tests/TestModified.h
index 518bea7c0..51c429871 100644
--- a/tests/TestModified.h
+++ b/tests/TestModified.h
@@ -29,7 +29,8 @@ private slots:
     void testSignals();
     void testGroupSets();
     void testEntrySets();
-    void testHistoryItem();
+    void testHistoryItems();
+    void testHistoryMaxSize();
 };
 
 #endif // KEEPASSX_TESTMODIFIED_H