diff --git a/src/configuredialog/configureplugins/configurepluginslistwidget.cpp b/src/configuredialog/configureplugins/configurepluginslistwidget.cpp
index 416f9b601..641749c84 100644
--- a/src/configuredialog/configureplugins/configurepluginslistwidget.cpp
+++ b/src/configuredialog/configureplugins/configurepluginslistwidget.cpp
@@ -316,7 +316,7 @@ void ConfigurePluginsListWidget::slotConfigureClicked(const QString &configureGr
                     const QString service = Akonadi::ServerManager::agentServiceName(Akonadi::ServerManager::Agent, data.mExtraInfo.at(0));
                     QDBusInterface interface(service, data.mExtraInfo.at(1));
                     if (interface.isValid()) {
-                        interface.call(QStringLiteral("showConfigureDialog"), (qlonglong)winId());
+                        interface.call(QStringLiteral("showConfigureDialog"), static_cast<qlonglong>(winId()));
                     } else {
                         qCDebug(KMAIL_LOG) << " interface does not exist when trying to configure the plugin";
                     }
diff --git a/src/dialog/addemailtoexistingcontactdialog.cpp b/src/dialog/addemailtoexistingcontactdialog.cpp
index 434bdb073..458f9e64b 100644
--- a/src/dialog/addemailtoexistingcontactdialog.cpp
+++ b/src/dialog/addemailtoexistingcontactdialog.cpp
@@ -33,6 +33,7 @@
 #include <QDialogButtonBox>
 #include <QVBoxLayout>
 #include <QPushButton>
+#include <KConfigGroup>
 
 AddEmailToExistingContactDialog::AddEmailToExistingContactDialog(QWidget *parent)
     : QDialog(parent)
diff --git a/src/folderarchive/folderarchiveaccountinfo.cpp b/src/folderarchive/folderarchiveaccountinfo.cpp
index 124fbded9..2090d88de 100644
--- a/src/folderarchive/folderarchiveaccountinfo.cpp
+++ b/src/folderarchive/folderarchiveaccountinfo.cpp
@@ -92,7 +92,7 @@ void FolderArchiveAccountInfo::readConfig(const KConfigGroup &config)
 {
     mInstanceName = config.readEntry(QStringLiteral("instanceName"));
     mArchiveTopLevelCollectionId = config.readEntry(QStringLiteral("topLevelCollectionId"), -1);
-    mArchiveType = static_cast<FolderArchiveType>(config.readEntry("folderArchiveType", (int)UniqueFolder));
+    mArchiveType = static_cast<FolderArchiveType>(config.readEntry("folderArchiveType", static_cast<int>(UniqueFolder)));
     mEnabled = config.readEntry("enabled", false);
     mKeepExistingStructure = config.readEntry("keepExistingStructure", false);
 }
@@ -106,7 +106,7 @@ void FolderArchiveAccountInfo::writeConfig(KConfigGroup &config)
         config.deleteEntry(QStringLiteral("topLevelCollectionId"));
     }
 
-    config.writeEntry(QStringLiteral("folderArchiveType"), (int)mArchiveType);
+    config.writeEntry(QStringLiteral("folderArchiveType"), static_cast<int>(mArchiveType));
     config.writeEntry(QStringLiteral("enabled"), mEnabled);
     config.writeEntry("keepExistingStructure", mKeepExistingStructure);
 }
diff --git a/src/folderarchive/folderarchivecache.cpp b/src/folderarchive/folderarchivecache.cpp
index 58330bc93..048a081f3 100644
--- a/src/folderarchive/folderarchivecache.cpp
+++ b/src/folderarchive/folderarchivecache.cpp
@@ -73,7 +73,6 @@ Akonadi::Collection::Id FolderArchiveCache::collectionId(FolderArchiveAccountInf
             } else {
                 return mCache.value(info->instanceName()).colId;
             }
-            break;
         }
         return mCache.value(info->instanceName()).colId;
     }
diff --git a/src/identity/identityaddvcarddialog.cpp b/src/identity/identityaddvcarddialog.cpp
index 6e4270e75..1f3390b45 100644
--- a/src/identity/identityaddvcarddialog.cpp
+++ b/src/identity/identityaddvcarddialog.cpp
@@ -56,12 +56,12 @@ IdentityAddVcardDialog::IdentityAddVcardDialog(const QStringList &shadowIdentiti
     QRadioButton *radio = new QRadioButton(i18n("&With empty fields"), this);
     radio->setChecked(true);
     vlay->addWidget(radio);
-    mButtonGroup->addButton(radio, (int)Empty);
+    mButtonGroup->addButton(radio, static_cast<int>(Empty));
 
     // row 2: radio button
     QRadioButton *fromExistingVCard = new QRadioButton(i18n("&From existing vCard"), this);
     vlay->addWidget(fromExistingVCard);
-    mButtonGroup->addButton(fromExistingVCard, (int)FromExistingVCard);
+    mButtonGroup->addButton(fromExistingVCard, static_cast<int>(FromExistingVCard));
 
     // row 3: KUrlRequester
     QHBoxLayout *hlay = new QHBoxLayout(); // inherits spacing
@@ -85,7 +85,7 @@ IdentityAddVcardDialog::IdentityAddVcardDialog(const QStringList &shadowIdentiti
     // row 4: radio button
     QRadioButton *duplicateExistingVCard = new QRadioButton(i18n("&Duplicate existing vCard"), this);
     vlay->addWidget(duplicateExistingVCard);
-    mButtonGroup->addButton(duplicateExistingVCard, (int)ExistingEntry);
+    mButtonGroup->addButton(duplicateExistingVCard, static_cast<int>(ExistingEntry));
 
     // row 5: combobox with existing identities and label
     hlay = new QHBoxLayout(); // inherits spacing
diff --git a/src/identity/identitydialog.cpp b/src/identity/identitydialog.cpp
index 9d2330a17..c434a1df3 100644
--- a/src/identity/identitydialog.cpp
+++ b/src/identity/identitydialog.cpp
@@ -131,7 +131,7 @@ public:
     };
 
     KeySelectionCombo(KeyType keyType, GpgME::Protocol protocol, QWidget *parent);
-    ~KeySelectionCombo();
+    ~KeySelectionCombo() override;
 
     void setIdentity(const QString &name, const QString &email);
 
@@ -151,7 +151,7 @@ class KeyGenerationJob : public QGpgME::Job
 
 public:
     KeyGenerationJob(const QString &name, const QString &email, KeySelectionCombo *parent);
-    ~KeyGenerationJob();
+    ~KeyGenerationJob() override;
 
     void slotCancel() override;
     void start();
diff --git a/src/identity/newidentitydialog.cpp b/src/identity/newidentitydialog.cpp
index f11bf5438..78724e6be 100644
--- a/src/identity/newidentitydialog.cpp
+++ b/src/identity/newidentitydialog.cpp
@@ -81,17 +81,17 @@ NewIdentityDialog::NewIdentityDialog(KIdentityManagement::IdentityManager *manag
     QRadioButton *radio = new QRadioButton(i18n("&With empty fields"), page);
     radio->setChecked(true);
     vlay->addWidget(radio);
-    mButtonGroup->addButton(radio, (int)Empty);
+    mButtonGroup->addButton(radio, static_cast<int>(Empty));
 
     // row 2: radio button
     radio = new QRadioButton(i18n("&Use System Settings values"), page);
     vlay->addWidget(radio);
-    mButtonGroup->addButton(radio, (int)ControlCenter);
+    mButtonGroup->addButton(radio, static_cast<int>(ControlCenter));
 
     // row 3: radio button
     radio = new QRadioButton(i18n("&Duplicate existing identity"), page);
     vlay->addWidget(radio);
-    mButtonGroup->addButton(radio, (int)ExistingEntry);
+    mButtonGroup->addButton(radio, static_cast<int>(ExistingEntry));
 
     // row 4: combobox with existing identities and label
     hlay = new QHBoxLayout(); // inherits spacing
diff --git a/src/main.cpp b/src/main.cpp
index 0e8456cc6..8b28a122d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -104,7 +104,7 @@ void KMailApplication::delayedInstanceCreation(const QStringList &args, const QS
 
 int main(int argc, char *argv[])
 {
-#if defined(Q_OS_UNIX) && QT_VERSION < QT_VERSION_CHECK(5, 9, 0)
+#if defined(Q_OS_UNIX) && QT_VERSION < QT_VERSION_CHECK(5, 11, 0)
     // enforce xcb plugin fix bug Bug 367598
     qputenv("QT_QPA_PLATFORM", "xcb");
 #endif