diff --git a/src/3rdparty/kmessagewidget/kmessagewidget.cpp b/src/3rdparty/kmessagewidget/kmessagewidget.cpp
index 29666a6c4..faa38ab1c 100644
--- a/src/3rdparty/kmessagewidget/kmessagewidget.cpp
+++ b/src/3rdparty/kmessagewidget/kmessagewidget.cpp
@@ -40,7 +40,7 @@ class KMessageWidgetPrivate
 public:
     void init(KMessageWidget *);
 
-    KMessageWidget *q;
+    KMessageWidget *q = nullptr;
     QFrame *content = nullptr;
     QLabel *iconLabel = nullptr;
     QLabel *textLabel = nullptr;
@@ -50,7 +50,7 @@ public:
     bool ignoreShowEventDoingAnimatedShow = false;
 
     KMessageWidget::MessageType messageType;
-    bool wordWrap;
+    bool wordWrap = false;
     QList<QToolButton *> buttons;
     QPixmap contentSnapShot;
 
diff --git a/src/3rdparty/qtlockedfile/qtlockedfile_unix.cpp b/src/3rdparty/qtlockedfile/qtlockedfile_unix.cpp
index d7460374f..cb4df4ef2 100644
--- a/src/3rdparty/qtlockedfile/qtlockedfile_unix.cpp
+++ b/src/3rdparty/qtlockedfile/qtlockedfile_unix.cpp
@@ -52,7 +52,7 @@ bool QtLockedFile::lock(LockMode mode, bool block)
     if (m_lock_mode != NoLock)
         unlock();
 
-    struct flock fl;
+    struct flock fl{};
     fl.l_whence = SEEK_SET;
     fl.l_start = 0;
     fl.l_len = 0;
@@ -82,7 +82,7 @@ bool QtLockedFile::unlock()
     if (!isLocked())
         return true;
 
-    struct flock fl;
+    struct flock fl{};
     fl.l_whence = SEEK_SET;
     fl.l_start = 0;
     fl.l_len = 0;
diff --git a/src/3rdparty/qtsingleapplication/qtsinglecoreapplication.h b/src/3rdparty/qtsingleapplication/qtsinglecoreapplication.h
index 139f9d858..ca22b57bb 100644
--- a/src/3rdparty/qtsingleapplication/qtsinglecoreapplication.h
+++ b/src/3rdparty/qtsingleapplication/qtsinglecoreapplication.h
@@ -55,7 +55,7 @@ Q_SIGNALS:
 
 private:
     QtLocalPeer* peer;
-    bool block;
+    bool block = false;
 };
 
 } // namespace SharedTools
diff --git a/src/cmd/cmd.cpp b/src/cmd/cmd.cpp
index 3826a681b..37c456dd1 100644
--- a/src/cmd/cmd.cpp
+++ b/src/cmd/cmd.cpp
@@ -71,16 +71,16 @@ struct CmdOptions
     QString user;
     QString password;
     QString proxy;
-    bool silent;
-    bool trustSSL;
-    bool useNetrc;
-    bool interactive;
-    bool ignoreHiddenFiles;
+    bool silent = false;
+    bool trustSSL = false;
+    bool useNetrc = false;
+    bool interactive = false;
+    bool ignoreHiddenFiles = false;
     QString exclude;
     QString unsyncedfolders;
-    int restartTimes;
-    int downlimit;
-    int uplimit;
+    int restartTimes = 0;
+    int downlimit = 0;
+    int uplimit = 0;
 };
 
 // we can't use csync_set_userdata because the SyncEngine sets it already.
@@ -118,7 +118,7 @@ private:
     DWORD mode = 0;
     HANDLE hStdin;
 #else
-    termios tios;
+    termios tios{};
 #endif
 };
 
diff --git a/src/common/utility.cpp b/src/common/utility.cpp
index 6613f0986..da968e53f 100644
--- a/src/common/utility.cpp
+++ b/src/common/utility.cpp
@@ -228,7 +228,7 @@ qint64 Utility::freeDiskSpace(const QString &path)
         return (qint64)stat.f_bavail * stat.f_frsize;
     }
 #elif defined(Q_OS_UNIX)
-    struct statvfs64 stat;
+    struct statvfs64 stat{};
     if (statvfs64(path.toLocal8Bit().data(), &stat) == 0) {
         return (qint64)stat.f_bavail * stat.f_frsize;
     }
diff --git a/src/gui/accountsettings.cpp b/src/gui/accountsettings.cpp
index 02a218e05..51ac7cd35 100644
--- a/src/gui/accountsettings.cpp
+++ b/src/gui/accountsettings.cpp
@@ -123,8 +123,8 @@ public:
     {
     }
 
-    QTreeView *folderList;
-    FolderStatusModel *model;
+    QTreeView *folderList = nullptr;
+    FolderStatusModel *model = nullptr;
 
 protected:
     bool eventFilter(QObject *watched, QEvent *event) override
@@ -1004,7 +1004,7 @@ void AccountSettings::slotSetSubFolderAvailability(Folder *folder, const QString
 void AccountSettings::displayMnemonic(const QString &mnemonic)
 {
     QDialog widget;
-    Ui_Dialog ui;
+    Ui_Dialog ui{};
     ui.setupUi(&widget);
     widget.setWindowTitle(tr("End-to-end encryption mnemonic"));
     ui.label->setText(
diff --git a/src/gui/accountsettings.h b/src/gui/accountsettings.h
index f3384ef76..7a3cd2df0 100644
--- a/src/gui/accountsettings.h
+++ b/src/gui/accountsettings.h
@@ -143,8 +143,8 @@ private:
     bool _wasDisabledBefore;
     AccountState *_accountState;
     UserInfo _userInfo;
-    QAction *_toggleSignInOutAction;
-    QAction *_addAccountAction;
+    QAction *_toggleSignInOutAction = nullptr;
+    QAction *_addAccountAction = nullptr;
 
     bool _menuShown;
 
diff --git a/src/gui/accountsetupcommandlinemanager.h b/src/gui/accountsetupcommandlinemanager.h
index 585627e85..156ab5d90 100644
--- a/src/gui/accountsetupcommandlinemanager.h
+++ b/src/gui/accountsetupcommandlinemanager.h
@@ -45,7 +45,7 @@ private:
     QUrl _serverUrl;
     QString _remoteDirPath;
     QString _localDirPath;
-    bool _isVfsEnabled;
+    bool _isVfsEnabled = false;
 };
 
 }
diff --git a/src/gui/creds/flow2auth.cpp b/src/gui/creds/flow2auth.cpp
index d0fbbca6b..1526921b8 100644
--- a/src/gui/creds/flow2auth.cpp
+++ b/src/gui/creds/flow2auth.cpp
@@ -91,7 +91,7 @@ void Flow2Auth::fetchNewToken(const TokenAction action)
 
     QObject::connect(job, &SimpleNetworkJob::finishedSignal, this, [this, action](QNetworkReply *reply) {
         auto jsonData = reply->readAll();
-        QJsonParseError jsonParseError;
+        QJsonParseError jsonParseError{};
         QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
         QString pollToken, pollEndpoint, loginUrl;
 
@@ -208,7 +208,7 @@ void Flow2Auth::slotPollTimerTimeout()
 
     QObject::connect(job, &SimpleNetworkJob::finishedSignal, this, [this](QNetworkReply *reply) {
         auto jsonData = reply->readAll();
-        QJsonParseError jsonParseError;
+        QJsonParseError jsonParseError{};
         QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
         QUrl serverUrl;
         QString loginName, appPassword;
diff --git a/src/gui/creds/flow2auth.h b/src/gui/creds/flow2auth.h
index 6b9440cfb..35efb721c 100644
--- a/src/gui/creds/flow2auth.h
+++ b/src/gui/creds/flow2auth.h
@@ -77,8 +77,8 @@ private:
     QString _pollToken;
     QString _pollEndpoint;
     QTimer _pollTimer;
-    qint64 _secondsLeft;
-    qint64 _secondsInterval;
+    qint64 _secondsLeft = 0LL;
+    qint64 _secondsInterval = 0LL;
     bool _isBusy;
     bool _hasToken;
     bool _enforceHttps = false;
diff --git a/src/gui/creds/oauth.cpp b/src/gui/creds/oauth.cpp
index 04b0e62f8..eaa25b97a 100644
--- a/src/gui/creds/oauth.cpp
+++ b/src/gui/creds/oauth.cpp
@@ -99,7 +99,7 @@ void OAuth::start()
                 job->setTimeout(qMin(30 * 1000ll, job->timeoutMsec()));
                 QObject::connect(job, &SimpleNetworkJob::finishedSignal, this, [this, socket](QNetworkReply *reply) {
                     auto jsonData = reply->readAll();
-                    QJsonParseError jsonParseError;
+                    QJsonParseError jsonParseError{};
                     QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
                     QString accessToken = json["access_token"].toString();
                     QString refreshToken = json["refresh_token"].toString();
diff --git a/src/gui/filedetails/shareemodel.h b/src/gui/filedetails/shareemodel.h
index 3bc1ec83c..94362d11b 100644
--- a/src/gui/filedetails/shareemodel.h
+++ b/src/gui/filedetails/shareemodel.h
@@ -92,7 +92,7 @@ private:
 
     QTimer _searchRateLimitingTimer;
 
-    AccountState *_accountState;
+    AccountState *_accountState = nullptr;
     QString _searchString;
     bool _shareItemIsFolder = false;
     bool _fetchOngoing = false;
diff --git a/src/gui/filedetails/sharemodel.h b/src/gui/filedetails/sharemodel.h
index 05e08fbdc..4e1198534 100644
--- a/src/gui/filedetails/sharemodel.h
+++ b/src/gui/filedetails/sharemodel.h
@@ -196,8 +196,8 @@ private:
     // We cannot pass objects instantiated in QML using smart pointers through the property interface
     // so we have to pass the pointer here. If we kill the dialog using a smart pointer then
     // these objects will be deallocated for the entire application. We do not want that!!
-    AccountState *_accountState;
-    Folder *_folder;
+    AccountState *_accountState = nullptr;
+    Folder *_folder = nullptr;
 
     QString _localPath;
     QString _sharePath;
diff --git a/src/gui/folderwizard.h b/src/gui/folderwizard.h
index fb60caca3..393c0ad33 100644
--- a/src/gui/folderwizard.h
+++ b/src/gui/folderwizard.h
@@ -70,7 +70,7 @@ protected slots:
 private:
     void changeStyle();
 
-    Ui_FolderWizardSourcePage _ui;
+    Ui_FolderWizardSourcePage _ui{};
     Folder::Map _folderMap;
     AccountPtr _account;
 };
@@ -114,7 +114,7 @@ private:
     LsColJob *runLsColJob(const QString &path);
     void recursiveInsert(QTreeWidgetItem *parent, QStringList pathTrail, QString path);
     bool selectByPath(QString path);
-    Ui_FolderWizardTargetPage _ui;
+    Ui_FolderWizardTargetPage _ui{};
     bool _warnWasVisible;
     AccountPtr _account;
     QTimer _lscolTimer;
diff --git a/src/gui/main.cpp b/src/gui/main.cpp
index d5d106efd..40af80ac0 100644
--- a/src/gui/main.cpp
+++ b/src/gui/main.cpp
@@ -116,7 +116,7 @@ int main(int argc, char **argv)
 // check a environment variable for core dumps
 #ifdef Q_OS_UNIX
     if (!qEnvironmentVariableIsEmpty("OWNCLOUD_CORE_DUMP")) {
-        struct rlimit core_limit;
+        struct rlimit core_limit{};
         core_limit.rlim_cur = RLIM_INFINITY;
         core_limit.rlim_max = RLIM_INFINITY;
 
diff --git a/src/gui/ocsjob.cpp b/src/gui/ocsjob.cpp
index 68c680b4d..09f7de00c 100644
--- a/src/gui/ocsjob.cpp
+++ b/src/gui/ocsjob.cpp
@@ -110,7 +110,7 @@ bool OcsJob::finished()
 {
     const QByteArray replyData = reply()->readAll();
 
-    QJsonParseError error;
+    QJsonParseError error{};
     QString message;
     int statusCode = 0;
     auto json = QJsonDocument::fromJson(replyData, &error);
diff --git a/src/gui/owncloudgui.h b/src/gui/owncloudgui.h
index ee38ad496..41c7895ef 100644
--- a/src/gui/owncloudgui.h
+++ b/src/gui/owncloudgui.h
@@ -120,9 +120,9 @@ private:
     QDBusConnection _bus;
 #endif
 
-    QAction *_actionNewAccountWizard;
-    QAction *_actionSettings;
-    QAction *_actionEstimate;
+    QAction *_actionNewAccountWizard = nullptr;
+    QAction *_actionSettings = nullptr;
+    QAction *_actionEstimate = nullptr;
 
 
     QList<QAction *> _recentItemsActions;
diff --git a/src/gui/remotewipe.cpp b/src/gui/remotewipe.cpp
index 8a1a0b06d..73af19f71 100644
--- a/src/gui/remotewipe.cpp
+++ b/src/gui/remotewipe.cpp
@@ -70,7 +70,7 @@ void RemoteWipe::startCheckJobWithAppPassword(QString pwd){
 void RemoteWipe::checkJobSlot()
 {
     auto jsonData = _networkReplyCheck->readAll();
-    QJsonParseError jsonParseError;
+    QJsonParseError jsonParseError{};
     QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
     bool wipe = false;
 
@@ -148,7 +148,7 @@ void RemoteWipe::notifyServerSuccessJob(AccountState *accountState, bool dataWip
 void RemoteWipe::notifyServerSuccessJobSlot()
 {
     auto jsonData = _networkReplySuccess->readAll();
-    QJsonParseError jsonParseError;
+    QJsonParseError jsonParseError{};
     QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
     if (_networkReplySuccess->error() != QNetworkReply::NoError ||
             jsonParseError.error != QJsonParseError::NoError) {
diff --git a/src/gui/selectivesyncdialog.h b/src/gui/selectivesyncdialog.h
index d44b957c5..acf8a6f4b 100644
--- a/src/gui/selectivesyncdialog.h
+++ b/src/gui/selectivesyncdialog.h
@@ -111,9 +111,9 @@ public:
 private:
     void init(const AccountPtr &account);
 
-    SelectiveSyncWidget *_selectiveSync;
+    SelectiveSyncWidget *_selectiveSync = nullptr;
 
     Folder *_folder;
-    QPushButton *_okButton;
+    QPushButton *_okButton = nullptr;
 };
 }
diff --git a/src/gui/socketapi/socketapi.cpp b/src/gui/socketapi/socketapi.cpp
index add45e0a9..9facf93a3 100644
--- a/src/gui/socketapi/socketapi.cpp
+++ b/src/gui/socketapi/socketapi.cpp
@@ -411,7 +411,7 @@ void SocketApi::slotReadSocket()
                 socketApiJob->reject(QStringLiteral("command not found"));
             }
         } else if (command.startsWith("V2/")) {
-            QJsonParseError error;
+            QJsonParseError error{};
             const auto json = QJsonDocument::fromJson(argument.toUtf8(), &error).object();
             if (error.error != QJsonParseError::NoError) {
                 qCWarning(lcSocketApi()) << "Invalid json" << argument.toString() << error.errorString();
diff --git a/src/gui/wizard/flow2authwidget.h b/src/gui/wizard/flow2authwidget.h
index cc1b01d57..a90fcbf49 100644
--- a/src/gui/wizard/flow2authwidget.h
+++ b/src/gui/wizard/flow2authwidget.h
@@ -50,7 +50,7 @@ signals:
 private:
     Account *_account = nullptr;
     QScopedPointer<Flow2Auth> _asyncAuth;
-    Ui_Flow2AuthWidget _ui;
+    Ui_Flow2AuthWidget _ui{};
 
 protected slots:
     void slotOpenBrowser();
diff --git a/src/gui/wizard/owncloudadvancedsetuppage.h b/src/gui/wizard/owncloudadvancedsetuppage.h
index 4de4b593e..2c0f23bb4 100644
--- a/src/gui/wizard/owncloudadvancedsetuppage.h
+++ b/src/gui/wizard/owncloudadvancedsetuppage.h
@@ -87,7 +87,7 @@ private:
     // TODO: remove when UX decision is made
     void refreshVirtualFilesAvailibility(const QString &path);
 
-    Ui_OwncloudAdvancedSetupPage _ui;
+    Ui_OwncloudAdvancedSetupPage _ui{};
     bool _checking = false;
     bool _created = false;
     bool _localFolderValid = false;
diff --git a/src/gui/wizard/owncloudoauthcredspage.h b/src/gui/wizard/owncloudoauthcredspage.h
index 339e97b02..2702aa330 100644
--- a/src/gui/wizard/owncloudoauthcredspage.h
+++ b/src/gui/wizard/owncloudoauthcredspage.h
@@ -56,7 +56,7 @@ public:
     QString _token;
     QString _refreshToken;
     QScopedPointer<OAuth> _asyncAuth;
-    Ui_OwncloudOAuthCredsPage _ui;
+    Ui_OwncloudOAuthCredsPage _ui{};
 
 protected slots:
     void slotOpenBrowser();
diff --git a/src/gui/wizard/owncloudsetuppage.h b/src/gui/wizard/owncloudsetuppage.h
index 590bc289f..e9c5da0d2 100644
--- a/src/gui/wizard/owncloudsetuppage.h
+++ b/src/gui/wizard/owncloudsetuppage.h
@@ -78,7 +78,7 @@ private:
     void customizeStyle();
     void setupServerAddressDescriptionLabel();
 
-    Ui_OwncloudSetupPage _ui;
+    Ui_OwncloudSetupPage _ui{};
 
     QString _oCUrl;
     QString _ocUser;
diff --git a/src/gui/wizard/owncloudwizard.h b/src/gui/wizard/owncloudwizard.h
index c720ab0ed..a586ee261 100644
--- a/src/gui/wizard/owncloudwizard.h
+++ b/src/gui/wizard/owncloudwizard.h
@@ -125,7 +125,7 @@ private:
     OwncloudOAuthCredsPage *_browserCredsPage;
     Flow2AuthCredsPage *_flow2CredsPage;
     OwncloudAdvancedSetupPage *_advancedSetupPage;
-    OwncloudWizardResultPage *_resultPage;
+    OwncloudWizardResultPage *_resultPage = nullptr;
     AbstractCredentialsWizardPage *_credentialsPage = nullptr;
     WebViewPage *_webViewPage = nullptr;
 
diff --git a/src/gui/wizard/webviewpage.h b/src/gui/wizard/webviewpage.h
index 23667975e..cbb6959ec 100644
--- a/src/gui/wizard/webviewpage.h
+++ b/src/gui/wizard/webviewpage.h
@@ -40,7 +40,7 @@ private:
     QString _user;
     QString _pass;
 
-    bool _useSystemProxy;
+    bool _useSystemProxy = false;
 
     QSize _originalWizardSize;
 };
diff --git a/src/libsync/bandwidthmanager.h b/src/libsync/bandwidthmanager.h
index 15e08f997..dac0d78a1 100644
--- a/src/libsync/bandwidthmanager.h
+++ b/src/libsync/bandwidthmanager.h
@@ -96,7 +96,7 @@ private:
     GETFileJob *_relativeLimitCurrentMeasuredJob;
 
     // for measuring how much progress we made at start
-    qint64 _relativeDownloadLimitProgressAtMeasuringRestart;
+    qint64 _relativeDownloadLimitProgressAtMeasuringRestart = 0LL;
 
     qint64 _currentDownloadLimit;
 };
diff --git a/src/libsync/clientsideencryptionjobs.cpp b/src/libsync/clientsideencryptionjobs.cpp
index 2e52a02a9..843419fbc 100644
--- a/src/libsync/clientsideencryptionjobs.cpp
+++ b/src/libsync/clientsideencryptionjobs.cpp
@@ -54,7 +54,7 @@ bool GetMetadataApiJob::finished()
         emit error(_fileId, retCode);
         return true;
     }
-    QJsonParseError error;
+    QJsonParseError error{};
     auto json = QJsonDocument::fromJson(reply()->readAll(), &error);
     emit jsonReceived(json, reply()->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt());
     return true;
@@ -285,7 +285,7 @@ bool LockEncryptFolderApiJob::finished()
         return true;
     }
 
-    QJsonParseError error;
+    QJsonParseError error{};
     const auto json = QJsonDocument::fromJson(reply()->readAll(), &error);
     const auto obj = json.object().toVariantMap();
     const auto token = obj["ocs"].toMap()["data"].toMap()["e2e-token"].toByteArray();
@@ -364,7 +364,7 @@ bool StorePrivateKeyApiJob::finished()
     if (retCode != 200)
         qCInfo(lcStorePrivateKeyApiJob()) << "Sending private key ended with"  << path() << errorString() << retCode;
 
-    QJsonParseError error;
+    QJsonParseError error{};
     auto json = QJsonDocument::fromJson(reply()->readAll(), &error);
     emit jsonReceived(json, reply()->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt());
     return true;
@@ -401,7 +401,7 @@ bool SignPublicKeyApiJob::finished()
 {
     qCInfo(lcStorePrivateKeyApiJob()) << "Sending CSR ended with"  << path() << errorString() << reply()->attribute(QNetworkRequest::HttpStatusCodeAttribute);
 
-    QJsonParseError error;
+    QJsonParseError error{};
     auto json = QJsonDocument::fromJson(reply()->readAll(), &error);
     emit jsonReceived(json, reply()->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt());
     return true;
diff --git a/src/libsync/clientsideencryptionjobs.h b/src/libsync/clientsideencryptionjobs.h
index f5cf6fbb6..7fcbac10d 100644
--- a/src/libsync/clientsideencryptionjobs.h
+++ b/src/libsync/clientsideencryptionjobs.h
@@ -193,7 +193,7 @@ signals:
 private:
     QByteArray _fileId;
     QByteArray _token;
-    QBuffer *_tokenBuf;
+    QBuffer *_tokenBuf = nullptr;
     QPointer<SyncJournalDb> _journalDb;
 };
 
diff --git a/src/libsync/creds/httpcredentials.cpp b/src/libsync/creds/httpcredentials.cpp
index 21ec6b823..fe570897a 100644
--- a/src/libsync/creds/httpcredentials.cpp
+++ b/src/libsync/creds/httpcredentials.cpp
@@ -430,7 +430,7 @@ bool HttpCredentials::refreshAccessToken()
     job->setTimeout(qMin(30 * 1000ll, job->timeoutMsec()));
     QObject::connect(job, &SimpleNetworkJob::finishedSignal, this, [this](QNetworkReply *reply) {
         auto jsonData = reply->readAll();
-        QJsonParseError jsonParseError;
+        QJsonParseError jsonParseError{};
         QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
         QString accessToken = json["access_token"].toString();
         if (jsonParseError.error != QJsonParseError::NoError || json.isEmpty()) {
diff --git a/src/libsync/creds/keychainchunk.h b/src/libsync/creds/keychainchunk.h
index b6bc50e45..8e09ba66a 100644
--- a/src/libsync/creds/keychainchunk.h
+++ b/src/libsync/creds/keychainchunk.h
@@ -74,7 +74,7 @@ public:
 
 protected:
     QString _serviceName;
-    Account *_account;
+    Account *_account = nullptr;
     QString _key;
     bool _insecureFallback = false;
     bool _autoDelete = true;
diff --git a/src/libsync/networkjobs.cpp b/src/libsync/networkjobs.cpp
index 19951674d..f1f73bdfa 100644
--- a/src/libsync/networkjobs.cpp
+++ b/src/libsync/networkjobs.cpp
@@ -530,7 +530,7 @@ bool CheckServerJob::finished()
         qCWarning(lcCheckServerJob) << "error: status.php replied " << httpStatus << body;
         emit instanceNotFound(reply());
     } else {
-        QJsonParseError error;
+        QJsonParseError error{};
         auto status = QJsonDocument::fromJson(body, &error);
         // empty or invalid response
         if (error.error != QJsonParseError::NoError || status.isNull()) {
@@ -862,7 +862,7 @@ bool JsonApiJob::finished()
     if(reply()->rawHeaderList().contains("ETag"))
         emit etagResponseHeaderReceived(reply()->rawHeader("ETag"), statusCode);
 
-    QJsonParseError error;
+    QJsonParseError error{};
     auto json = QJsonDocument::fromJson(jsonStr.toUtf8(), &error);
     // empty or invalid response and status code is != 304 because jsonStr is expected to be empty
     if ((error.error != QJsonParseError::NoError || json.isNull()) && httpStatusCode != notModifiedStatusCode) {
diff --git a/src/libsync/progressdispatcher.cpp b/src/libsync/progressdispatcher.cpp
index 85b99fb66..abc820fb5 100644
--- a/src/libsync/progressdispatcher.cpp
+++ b/src/libsync/progressdispatcher.cpp
@@ -369,7 +369,7 @@ void ProgressInfo::recomputeCompletedSize()
 
 ProgressInfo::Estimates ProgressInfo::Progress::estimates() const
 {
-    Estimates est;
+    Estimates est{};
     est.estimatedBandwidth = _progressPerSec;
     if (_progressPerSec != 0) {
         est.estimatedEta = qRound64(static_cast<double>(_total - _completed) / _progressPerSec) * 1000;
diff --git a/src/libsync/progressdispatcher.h b/src/libsync/progressdispatcher.h
index 3276586cd..9ff71b7e3 100644
--- a/src/libsync/progressdispatcher.h
+++ b/src/libsync/progressdispatcher.h
@@ -227,11 +227,11 @@ private:
     Progress _fileProgress;
 
     // All size from completed jobs only.
-    qint64 _totalSizeOfCompletedJobs;
+    qint64 _totalSizeOfCompletedJobs = 0LL;
 
     // The fastest observed rate of files per second in this sync.
-    double _maxFilesPerSecond;
-    double _maxBytesPerSecond;
+    double _maxFilesPerSecond = 0.0;
+    double _maxBytesPerSecond = 0.0;
 };
 
 namespace Progress {
diff --git a/src/libsync/propagateupload.cpp b/src/libsync/propagateupload.cpp
index 829dc529d..658c9060d 100644
--- a/src/libsync/propagateupload.cpp
+++ b/src/libsync/propagateupload.cpp
@@ -130,7 +130,7 @@ bool PollJob::finished()
     }
 
     QByteArray jsonData = reply()->readAll().trimmed();
-    QJsonParseError jsonParseError;
+    QJsonParseError jsonParseError{};
     QJsonObject json = QJsonDocument::fromJson(jsonData, &jsonParseError).object();
     qCInfo(lcPollJob) << ">" << jsonData << "<" << reply()->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt() << json << jsonParseError.errorString();
     if (jsonParseError.error != QJsonParseError::NoError) {
diff --git a/src/libsync/userstatusconnector.h b/src/libsync/userstatusconnector.h
index 1af208ea0..20d12347f 100644
--- a/src/libsync/userstatusconnector.h
+++ b/src/libsync/userstatusconnector.h
@@ -94,7 +94,7 @@ private:
     QString _message;
     QString _icon;
     OnlineStatus _state = OnlineStatus::Online;
-    bool _messagePredefined;
+    bool _messagePredefined = false;
     Optional<ClearAt> _clearAt;
 };
 
diff --git a/test/syncenginetestutils.h b/test/syncenginetestutils.h
index 7f1c3e2f6..8d24e2863 100644
--- a/test/syncenginetestutils.h
+++ b/test/syncenginetestutils.h
@@ -304,8 +304,8 @@ class FakeGetReply : public FakeReply
     Q_OBJECT
 public:
     const FileInfo *fileInfo;
-    char payload;
-    int size;
+    char payload = 0;
+    int size = 0;
     bool aborted = false;
 
     FakeGetReply(FileInfo &remoteRootFileInfo, QNetworkAccessManager::Operation op, const QNetworkRequest &request, QObject *parent);
diff --git a/test/testchecksumvalidator.cpp b/test/testchecksumvalidator.cpp
index 10be1f0d7..3d2bb076d 100644
--- a/test/testchecksumvalidator.cpp
+++ b/test/testchecksumvalidator.cpp
@@ -28,8 +28,8 @@ using namespace OCC::Utility;
         ValidateChecksumHeader::FailureReason _expectedFailureReason = ValidateChecksumHeader::FailureReason::Success;
         QByteArray     _expected;
         QByteArray     _expectedType;
-        bool           _successDown;
-        bool           _errorSeen;
+        bool           _successDown = false;
+        bool           _errorSeen = false;
 
     public slots:
 
diff --git a/test/testxmlparse.cpp b/test/testxmlparse.cpp
index 201c3a449..8bc987a52 100644
--- a/test/testxmlparse.cpp
+++ b/test/testxmlparse.cpp
@@ -15,7 +15,7 @@ class TestXmlParse : public QObject
     Q_OBJECT
 
 private:
-  bool _success;
+  bool _success = false;
   QStringList _subdirs;
   QStringList _items;