diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index 56d9e0a011..02501e00f4 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -4324,10 +4324,16 @@ bool QString::contains(const QRegularExpression &re, QRegularExpressionMatch *rm
     Returns the number of times the regular expression \a re matches
     in the string.
 
-    This function counts overlapping matches, so in the example
-    below, there are four instances of "ana" or "ama":
+    For historical reasons, this function counts overlapping matches,
+    so in the example below, there are four instances of "ana" or
+    "ama":
 
     \snippet qstring/main.cpp 95
+
+    This behavior is different from simply iterating over the matches
+    in the string using QRegularExpressionMatchIterator.
+
+    \sa QRegularExpression::globalMatch()
 */
 qsizetype QString::count(const QRegularExpression &re) const
 {
@@ -4338,7 +4344,7 @@ qsizetype QString::count(const QRegularExpression &re) const
     qsizetype count = 0;
     qsizetype index = -1;
     qsizetype len = length();
-    while (index < len - 1) {
+    while (index <= len - 1) {
         QRegularExpressionMatch match = re.match(*this, index + 1);
         if (!match.hasMatch())
             break;
diff --git a/tests/auto/corelib/text/qstring/tst_qstring.cpp b/tests/auto/corelib/text/qstring/tst_qstring.cpp
index 04a4469a7d..7c965129f0 100644
--- a/tests/auto/corelib/text/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/text/qstring/tst_qstring.cpp
@@ -1714,6 +1714,7 @@ void tst_QString::count()
     QCOMPARE(a.count("FG",Qt::CaseInsensitive),3);
     QCOMPARE(a.count( QString(), Qt::CaseInsensitive), 16);
     QCOMPARE(a.count( "", Qt::CaseInsensitive), 16);
+    QCOMPARE(a.count(QRegularExpression("")), 16);
     QCOMPARE(a.count(QRegularExpression("[FG][HI]")), 1);
     QCOMPARE(a.count(QRegularExpression("[G][HE]")), 2);
     QTest::ignoreMessage(QtWarningMsg, "QString::count: invalid QRegularExpression object");