diff --git a/src/common.cpp b/src/common.cpp
index 7474a3591..3ea0e3755 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -467,20 +467,7 @@ void bringToFront(QWidget *widget, bool)
     QWidget *w = widget->window();
 
 #ifdef HAVE_X11
-    if (QX11Info::isPlatformX11()) {
-        // If we're not on the current desktop, do the hide/show trick
-        long   dsk, curr_dsk;
-        Window win = w->winId();
-        if (X11WindowSystem::instance()->desktopOfWindow(&win, &dsk)
-            && X11WindowSystem::instance()->currentDesktop(&curr_dsk)) {
-            // qDebug() << "bringToFront current desktop=" << curr_dsk << " windowDesktop=" << dsk;
-            if ((dsk != curr_dsk) && (dsk != -1)) { // second condition for sticky windows
-                w->hide();
-            }
-        }
-    }
-
-    // FIXME: multi-desktop hacks for Win and Mac required
+    X11WindowSystem::instance()->bringToFront(w);
 #endif
 
     if (w->isMaximized()) {
diff --git a/src/common.h b/src/common.h
index ab586fd7b..e863d4fc2 100644
--- a/src/common.h
+++ b/src/common.h
@@ -165,8 +165,7 @@ TabbableWidget *findActiveTab();
 #include "x11windowsystem.h"
 #define X11WM_CLASS(x)                                                                                                 \
     {                                                                                                                  \
-        if (QX11Info::isPlatformX11())                                                                                 \
-            X11WindowSystem::instance()->x11wmClass(winId(), (x));                                                     \
+        X11WindowSystem::instance()->x11wmClass(winId(), (x));                                                     \
     };
 #else
 #define X11WM_CLASS(x) /* dummy */
diff --git a/src/contactmanager/contactmanagermodel.cpp b/src/contactmanager/contactmanagermodel.cpp
index 6e1757afe..1979bc5da 100644
--- a/src/contactmanager/contactmanagermodel.cpp
+++ b/src/contactmanager/contactmanagermodel.cpp
@@ -251,7 +251,7 @@ void ContactManagerModel::invertByMatch(int columnIndex, int matchType, const QS
     for (UserListItem *u : std::as_const(_userList)) {
         data = userFieldString(u, columnRole);
         if ((matchType == ContactManagerModel::SimpleMatch && str == data)
-            || (matchType == ContactManagerModel::RegexpMatch && reg.indexIn(data) != -1)) {
+            || (matchType == ContactManagerModel::RegexpMatch && reg.match(data).hasMatch())) {
             QString jid = u->jid().full();
             if (checks.contains(jid)) {
                 checks.remove(jid);
diff --git a/src/mainwin.cpp b/src/mainwin.cpp
index 897047c14..8d719772f 100644
--- a/src/mainwin.cpp
+++ b/src/mainwin.cpp
@@ -1578,9 +1578,10 @@ void MainWin::toggleVisible(bool fromTray)
         }
 #elif defined(HAVE_X11)
         Q_UNUSED(fromTray);
-        if (QX11Info::isPlatformX11()) {
+        auto x11 = X11WindowSystem::instance();
+        if (x11->isValid()) {
             hidden = isHidden()
-                || X11WindowSystem::instance()->isWindowObscured(
+                || x11->isWindowObscured(
                     this, PsiOptions::instance()->getOption("options.ui.contactlist.always-on-top").toBool());
         } else {
             hidden = isHidden() || !isActiveWindow();
diff --git a/src/mcmdmanager.cpp b/src/mcmdmanager.cpp
index 0665cf6ee..231412bca 100644
--- a/src/mcmdmanager.cpp
+++ b/src/mcmdmanager.cpp
@@ -21,6 +21,7 @@
 #include "mcmdmanager.h"
 
 #include <QDebug>
+#include <QRegularExpression>
 
 MCmdSimpleState::MCmdSimpleState(QString name, QString prompt) : name_(name), prompt_(prompt), flags_(0) { }
 
diff --git a/src/msgmle.cpp b/src/msgmle.cpp
index 2fdb7bc98..1ca20fba1 100644
--- a/src/msgmle.cpp
+++ b/src/msgmle.cpp
@@ -105,8 +105,9 @@ public slots:
                 return;
             } else {
                 QRegularExpression capitalizeAfter("(?:^[^.][.]+\\s+)|(?:\\s*[^.]{2,}[.]+\\s+)|(?:[!?]\\s+)");
-                int     index = te_->toPlainText().lastIndexOf(capitalizeAfter);
-                if (index != -1 && index == pos - capitalizeAfter.matchedLength()) {
+                QRegularExpressionMatch match;
+                int     index = te_->toPlainText().lastIndexOf(capitalizeAfter, 0, &match);
+                if (index != -1 && index == pos - match.capturedLength()) {
                     capitalizeNext_ = true;
                 }
             }
diff --git a/src/x11windowsystem.cpp b/src/x11windowsystem.cpp
index e9b124716..ad81defca 100644
--- a/src/x11windowsystem.cpp
+++ b/src/x11windowsystem.cpp
@@ -7,6 +7,10 @@
 const long       MAX_PROP_SIZE              = 100000;
 X11WindowSystem *X11WindowSystem::_instance = nullptr;
 
+bool X11WindowSystem::isValid() const {
+    return QX11Info::isPlatformX11();
+}
+
 void X11WindowSystem::x11wmClass(WId wid, QString resName)
 {
 #if defined(LIMIT_X11_USAGE)
@@ -30,6 +34,24 @@ void X11WindowSystem::x11wmClass(WId wid, QString resName)
     XFree(classhint.res_class);
 }
 
+void X11WindowSystem::bringToFront(QWidget *w)
+{
+    if (QX11Info::isPlatformX11()) {
+        // If we're not on the current desktop, do the hide/show trick
+        long   dsk, curr_dsk;
+        Window win = w->winId();
+        if (X11WindowSystem::instance()->desktopOfWindow(&win, &dsk)
+            && X11WindowSystem::instance()->currentDesktop(&curr_dsk)) {
+            // qDebug() << "bringToFront current desktop=" << curr_dsk << " windowDesktop=" << dsk;
+            if ((dsk != curr_dsk) && (dsk != -1)) { // second condition for sticky windows
+                w->hide();
+            }
+        }
+    }
+
+    // FIXME: multi-desktop hacks for Win and Mac required
+}
+
 //>>>-- Nathaniel Gray -- Caltech Computer Science ------>
 //>>>-- Mojave Project -- http://mojave.cs.caltech.edu -->
 // Copied from http://www.nedit.org/archives/discuss/2002-Aug/0386.html
diff --git a/src/x11windowsystem.h b/src/x11windowsystem.h
index 3c279e8db..3431753cc 100644
--- a/src/x11windowsystem.h
+++ b/src/x11windowsystem.h
@@ -4,7 +4,6 @@
 #include <QRect>
 #include <QSet>
 #include <QWidget>
-//#include <QX11Info>
 #include <QtCore>
 
 // TODO: Find a way to include Xlib here and not redefine Atom and Window types
@@ -36,6 +35,7 @@ class X11WindowSystem {
 
 public:
     static X11WindowSystem *instance();
+    bool                    isValid() const;
     QRect                   windowRect(Window win);
     bool                    isWindowObscured(QWidget *widget, bool alwaysOnTop);
     bool                    windowHasOnlyTypes(Window win, const QSet<Atom> &allowedTypes);
@@ -43,6 +43,7 @@ class X11WindowSystem {
     bool                    currentDesktop(long *desktop);
     bool                    desktopOfWindow(Window *window, long *desktop);
     void                    x11wmClass(WId wid, QString resName);
+    void                    bringToFront(QWidget *w);
 };
 
 #endif // X11WINDOWSYSTEM_H
diff --git a/version b/version
index b3b53d1d8..ee224dd2b 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-1.5.1664 (2024-03-14, d668704d)
+1.5.1665 (2024-03-14, 694f4289)