diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index 28e8b6be83..e12cf1f910 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -3391,15 +3391,11 @@ QString QString::right(int n) const
 
 QString QString::mid(int position, int n) const
 {
-    if (d == &shared_null.str || position > d->size)
+    if (position > d->size)
         return QString();
-    if (n < 0)
-        n = d->size - position;
-    if (position < 0) {
-        n += position;
+    if (position < 0)
         position = 0;
-    }
-    if (n + position > d->size)
+    if (n < 0 || n > d->size - position)
         n = d->size - position;
     if (position == 0 && n == d->size)
         return *this;
@@ -8061,15 +8057,11 @@ QStringRef QString::rightRef(int n) const
 
 QStringRef QString::midRef(int position, int n) const
 {
-    if (d == &shared_null.str || position > d->size)
+    if (position > d->size)
         return QStringRef();
-    if (n < 0)
-        n = d->size - position;
-    if (position < 0) {
-        n += position;
+    if (position < 0)
         position = 0;
-    }
-    if (n + position > d->size)
+    if (n < 0 || n > d->size - position)
         n = d->size - position;
     return QStringRef(this, position, n);
 }
diff --git a/tests/auto/corelib/tools/qstring/tst_qstring.cpp b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
index 37d80afd34..7dd801b50b 100644
--- a/tests/auto/corelib/tools/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
@@ -1429,16 +1429,51 @@ void tst_QString::mid()
     QVERIFY(a.mid(9999).isNull());
     QVERIFY(a.mid(9999,1).isNull());
 
+    QCOMPARE(a.mid(-1, 6), QString("ABCDEF"));
+    QCOMPARE(a.mid(-100, 6), QString("ABCDEF"));
+    QVERIFY(a.mid(INT_MAX).isNull());
+    QVERIFY(a.mid(INT_MAX, INT_MAX).isNull());
+    QCOMPARE(a.mid(-5, INT_MAX), a);
+    QCOMPARE(a.mid(-1, INT_MAX), a);
+    QCOMPARE(a.mid(0, INT_MAX), a);
+    QCOMPARE(a.mid(1, INT_MAX), QString("BCDEFGHIEfGEFG"));
+    QCOMPARE(a.mid(5, INT_MAX), QString("FGHIEfGEFG"));
+    QVERIFY(a.mid(20, INT_MAX).isNull());
+    QCOMPARE(a.mid(-1, -1), a);
+
     QString n;
     QVERIFY(n.mid(3,3).isNull());
     QVERIFY(n.mid(0,0).isNull());
     QVERIFY(n.mid(9999,0).isNull());
     QVERIFY(n.mid(9999,1).isNull());
 
+    QVERIFY(n.mid(-1, 6).isNull());
+    QVERIFY(n.mid(-100, 6).isNull());
+    QVERIFY(n.mid(INT_MAX).isNull());
+    QVERIFY(n.mid(INT_MAX, INT_MAX).isNull());
+    QVERIFY(n.mid(-5, INT_MAX).isNull());
+    QVERIFY(n.mid(-1, INT_MAX).isNull());
+    QVERIFY(n.mid(0, INT_MAX).isNull());
+    QVERIFY(n.mid(1, INT_MAX).isNull());
+    QVERIFY(n.mid(5, INT_MAX).isNull());
+    QVERIFY(n.mid(20, INT_MAX).isNull());
+    QVERIFY(n.mid(-1, -1).isNull());
+
     QString x = "Nine pineapples";
     QCOMPARE(x.mid(5, 4), QString("pine"));
     QCOMPARE(x.mid(5), QString("pineapples"));
 
+    QCOMPARE(x.mid(-1, 6), QString("Nine p"));
+    QCOMPARE(x.mid(-100, 6), QString("Nine p"));
+    QVERIFY(x.mid(INT_MAX).isNull());
+    QVERIFY(x.mid(INT_MAX, INT_MAX).isNull());
+    QCOMPARE(x.mid(-5, INT_MAX), x);
+    QCOMPARE(x.mid(-1, INT_MAX), x);
+    QCOMPARE(x.mid(0, INT_MAX), x);
+    QCOMPARE(x.mid(1, INT_MAX), QString("ine pineapples"));
+    QCOMPARE(x.mid(5, INT_MAX), QString("pineapples"));
+    QVERIFY(x.mid(20, INT_MAX).isNull());
+    QCOMPARE(x.mid(-1, -1), x);
 }
 
 void tst_QString::midRef()
@@ -1455,16 +1490,51 @@ void tst_QString::midRef()
     QVERIFY(a.midRef(9999).toString().isEmpty());
     QVERIFY(a.midRef(9999,1).toString().isEmpty());
 
+    QCOMPARE(a.midRef(-1, 6).toString(), QString("ABCDEF"));
+    QCOMPARE(a.midRef(-100, 6).toString(), QString("ABCDEF"));
+    QVERIFY(a.midRef(INT_MAX).isNull());
+    QVERIFY(a.midRef(INT_MAX, INT_MAX).isNull());
+    QCOMPARE(a.midRef(-5, INT_MAX).toString(), a);
+    QCOMPARE(a.midRef(-1, INT_MAX).toString(), a);
+    QCOMPARE(a.midRef(0, INT_MAX).toString(), a);
+    QCOMPARE(a.midRef(1, INT_MAX).toString(), QString("BCDEFGHIEfGEFG"));
+    QCOMPARE(a.midRef(5, INT_MAX).toString(), QString("FGHIEfGEFG"));
+    QVERIFY(a.midRef(20, INT_MAX).isNull());
+    QCOMPARE(a.midRef(-1, -1).toString(), a);
+
     QString n;
     QVERIFY(n.midRef(3,3).toString().isEmpty());
     QVERIFY(n.midRef(0,0).toString().isEmpty());
     QVERIFY(n.midRef(9999,0).toString().isEmpty());
     QVERIFY(n.midRef(9999,1).toString().isEmpty());
 
+    QVERIFY(n.midRef(-1, 6).isNull());
+    QVERIFY(n.midRef(-100, 6).isNull());
+    QVERIFY(n.midRef(INT_MAX).isNull());
+    QVERIFY(n.midRef(INT_MAX, INT_MAX).isNull());
+    QVERIFY(n.midRef(-5, INT_MAX).isNull());
+    QVERIFY(n.midRef(-1, INT_MAX).isNull());
+    QVERIFY(n.midRef(0, INT_MAX).isNull());
+    QVERIFY(n.midRef(1, INT_MAX).isNull());
+    QVERIFY(n.midRef(5, INT_MAX).isNull());
+    QVERIFY(n.midRef(20, INT_MAX).isNull());
+    QVERIFY(n.midRef(-1, -1).isNull());
+
     QString x = "Nine pineapples";
     QCOMPARE(x.midRef(5, 4).toString(), QString("pine"));
     QCOMPARE(x.midRef(5).toString(), QString("pineapples"));
 
+    QCOMPARE(x.midRef(-1, 6).toString(), QString("Nine p"));
+    QCOMPARE(x.midRef(-100, 6).toString(), QString("Nine p"));
+    QVERIFY(x.midRef(INT_MAX).isNull());
+    QVERIFY(x.midRef(INT_MAX, INT_MAX).isNull());
+    QCOMPARE(x.midRef(-5, INT_MAX).toString(), x);
+    QCOMPARE(x.midRef(-1, INT_MAX).toString(), x);
+    QCOMPARE(x.midRef(0, INT_MAX).toString(), x);
+    QCOMPARE(x.midRef(1, INT_MAX).toString(), QString("ine pineapples"));
+    QCOMPARE(x.midRef(5, INT_MAX).toString(), QString("pineapples"));
+    QVERIFY(x.midRef(20, INT_MAX).isNull());
+    QCOMPARE(x.midRef(-1, -1).toString(), x);
 }
 
 void tst_QString::stringRef()