diff --git a/src/corelib/compat/removed_api.cpp b/src/corelib/compat/removed_api.cpp
index 42f2ef97ea7..99402ed35d3 100644
--- a/src/corelib/compat/removed_api.cpp
+++ b/src/corelib/compat/removed_api.cpp
@@ -287,6 +287,18 @@ QT_WARNING_POP
 
 #include "qbuffer.h" // inline removed API
 
+#include "qbasictimer.h"
+
+void QBasicTimer::start(int msec, QObject *obj)
+{
+    start(qint64(msec), obj);
+}
+
+void QBasicTimer::start(int msec, Qt::TimerType timerType, QObject *obj)
+{
+    start(qint64(msec), timerType, obj);
+}
+
 #include "qenvironmentvariables.h"
 
 bool qputenv(const char *varName, const QByteArray &value)
diff --git a/src/corelib/kernel/qabstracteventdispatcher.h b/src/corelib/kernel/qabstracteventdispatcher.h
index 8cd7ae2983c..4026bde347a 100644
--- a/src/corelib/kernel/qabstracteventdispatcher.h
+++ b/src/corelib/kernel/qabstracteventdispatcher.h
@@ -26,8 +26,7 @@ public:
         Qt::TimerType timerType;
 
         inline TimerInfo(int id, int i, Qt::TimerType t)
-            : timerId(id), interval(i), timerType(t)
-        { }
+            : timerId(id), interval(i), timerType(t) { }
     };
 
     explicit QAbstractEventDispatcher(QObject *parent = nullptr);
diff --git a/src/corelib/kernel/qbasictimer.cpp b/src/corelib/kernel/qbasictimer.cpp
index d529920bb14..346154b1aaf 100644
--- a/src/corelib/kernel/qbasictimer.cpp
+++ b/src/corelib/kernel/qbasictimer.cpp
@@ -102,7 +102,7 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
-    \fn void QBasicTimer::start(int msec, QObject *object)
+    \fn void QBasicTimer::start(qint64 msec, QObject *object)
 
     Starts (or restarts) the timer with a \a msec milliseconds timeout. The
     timer will be a Qt::CoarseTimer. See Qt::TimerType for information on the
@@ -110,9 +110,12 @@ QT_BEGIN_NAMESPACE
 
     The given \a object will receive timer events.
 
+    \note In Qt versions prior to 6.5, \a msec was \c{int}, not
+    \c{qint64}.
+
     \sa stop(), isActive(), QObject::timerEvent(), Qt::CoarseTimer
  */
-void QBasicTimer::start(int msec, QObject *obj)
+void QBasicTimer::start(qint64 msec, QObject *obj)
 {
     start(msec, Qt::CoarseTimer, obj);
 }
@@ -126,9 +129,12 @@ void QBasicTimer::start(int msec, QObject *obj)
 
     \a obj will receive timer events.
 
+    \note In Qt versions prior to 6.5, \a msec was \c{int}, not
+    \c{qint64}.
+
     \sa stop(), isActive(), QObject::timerEvent(), Qt::TimerType
  */
-void QBasicTimer::start(int msec, Qt::TimerType timerType, QObject *obj)
+void QBasicTimer::start(qint64 msec, Qt::TimerType timerType, QObject *obj)
 {
     QAbstractEventDispatcher *eventDispatcher = QAbstractEventDispatcher::instance();
     if (Q_UNLIKELY(msec < 0)) {
diff --git a/src/corelib/kernel/qbasictimer.h b/src/corelib/kernel/qbasictimer.h
index e3a41822de5..13d48822f5a 100644
--- a/src/corelib/kernel/qbasictimer.h
+++ b/src/corelib/kernel/qbasictimer.h
@@ -31,9 +31,12 @@ public:
 
     bool isActive() const noexcept { return id != 0; }
     int timerId() const noexcept { return id; }
-
+#if QT_CORE_REMOVED_SINCE(6, 5)
     void start(int msec, QObject *obj);
     void start(int msec, Qt::TimerType timerType, QObject *obj);
+#endif
+    void start(qint64 msec, QObject *obj);
+    void start(qint64 msec, Qt::TimerType timerType, QObject *obj);
     void stop();
 };
 Q_DECLARE_TYPEINFO(QBasicTimer, Q_RELOCATABLE_TYPE);
diff --git a/src/corelib/kernel/qtimerinfo_unix.cpp b/src/corelib/kernel/qtimerinfo_unix.cpp
index 48ce893988d..288fb30d326 100644
--- a/src/corelib/kernel/qtimerinfo_unix.cpp
+++ b/src/corelib/kernel/qtimerinfo_unix.cpp
@@ -380,18 +380,17 @@ bool QTimerInfoList::timerWait(timespec &tm)
 }
 
 /*
-  Returns the timer's remaining time in milliseconds with the given timerId, or
-  null if there is nothing left. If the timer id is not found in the list, the
-  returned value will be -1. If the timer is overdue, the returned value will be 0.
+  Returns the timer's remaining time in milliseconds with the given timerId.
+  If the timer id is not found in the list, the returned value will be -1.
+  If the timer is overdue, the returned value will be 0.
 */
-int QTimerInfoList::timerRemainingTime(int timerId)
+qint64 QTimerInfoList::timerRemainingTime(int timerId)
 {
     timespec currentTime = updateCurrentTime();
     repairTimersIfNeeded();
     timespec tm = {0, 0};
 
-    for (int i = 0; i < count(); ++i) {
-        QTimerInfo *t = at(i);
+    for (const auto *t : *this) {
         if (t->id == timerId) {
             if (currentTime < t->timeout) {
                 // time to wait
diff --git a/src/corelib/kernel/qtimerinfo_unix_p.h b/src/corelib/kernel/qtimerinfo_unix_p.h
index 9e0c225a1eb..c33bddbd2f4 100644
--- a/src/corelib/kernel/qtimerinfo_unix_p.h
+++ b/src/corelib/kernel/qtimerinfo_unix_p.h
@@ -68,7 +68,7 @@ public:
     bool timerWait(timespec &);
     void timerInsert(QTimerInfo *);
 
-    int timerRemainingTime(int timerId);
+    qint64 timerRemainingTime(int timerId);
 
     void registerTimer(int timerId, qint64 interval, Qt::TimerType timerType, QObject *object);
     bool unregisterTimer(int timerId);