diff --git a/src/corelib/global/qflags.h b/src/corelib/global/qflags.h
index 275ab12800..cfe75c4eea 100644
--- a/src/corelib/global/qflags.h
+++ b/src/corelib/global/qflags.h
@@ -117,13 +117,13 @@ public:
         : i(initializer_list_helper(flags.begin(), flags.end())) {}
 #endif
 
-    inline QFlags &operator&=(int mask) { i &= mask; return *this; }
-    inline QFlags &operator&=(uint mask) { i &= mask; return *this; }
-    inline QFlags &operator&=(Enum mask) { i &= Int(mask); return *this; }
-    inline QFlags &operator|=(QFlags f) { i |= f.i; return *this; }
-    inline QFlags &operator|=(Enum f) { i |= Int(f); return *this; }
-    inline QFlags &operator^=(QFlags f) { i ^= f.i; return *this; }
-    inline QFlags &operator^=(Enum f) { i ^= Int(f); return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator&=(int mask) { i &= mask; return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator&=(uint mask) { i &= mask; return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator&=(Enum mask) { i &= Int(mask); return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator|=(QFlags f) { i |= f.i; return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator|=(Enum f) { i |= Int(f); return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator^=(QFlags f) { i ^= f.i; return *this; }
+    Q_DECL_RELAXED_CONSTEXPR inline QFlags &operator^=(Enum f) { i ^= Int(f); return *this; }
 
     Q_DECL_CONSTEXPR  inline operator Int() const { return i; }
 
diff --git a/tests/auto/corelib/global/qflags/qflags.pro b/tests/auto/corelib/global/qflags/qflags.pro
index 9e80d5634b..3f78bc045b 100644
--- a/tests/auto/corelib/global/qflags/qflags.pro
+++ b/tests/auto/corelib/global/qflags/qflags.pro
@@ -3,3 +3,4 @@ TARGET = tst_qflags
 QT = core testlib
 SOURCES = tst_qflags.cpp
 DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0
+contains(QT_CONFIG, c++11): CONFIG += c++11 c++14
diff --git a/tests/auto/corelib/global/qflags/tst_qflags.cpp b/tests/auto/corelib/global/qflags/tst_qflags.cpp
index 4c74ac166b..15fe93298d 100644
--- a/tests/auto/corelib/global/qflags/tst_qflags.cpp
+++ b/tests/auto/corelib/global/qflags/tst_qflags.cpp
@@ -94,6 +94,16 @@ void tst_QFlags::testFlagMultiBits() const
 
 template <unsigned int N, typename T> bool verifyConstExpr(T n) { return n == N; }
 
+Q_DECL_RELAXED_CONSTEXPR Qt::MouseButtons testRelaxedConstExpr()
+{
+    Qt::MouseButtons value;
+    value = Qt::LeftButton | Qt::RightButton;
+    value |= Qt::MiddleButton;
+    value &= ~Qt::LeftButton;
+    value ^= Qt::RightButton;
+    return value;
+}
+
 void tst_QFlags::constExpr()
 {
 #ifdef Q_COMPILER_CONSTEXPR
@@ -115,6 +125,10 @@ void tst_QFlags::constExpr()
     QVERIFY(verifyConstExpr<Qt::MouseButtons(Qt::RightButton) | 0xff>(0xff));
 
     QVERIFY(!verifyConstExpr<Qt::RightButton>(!Qt::MouseButtons(Qt::LeftButton)));
+
+#if defined(__cpp_constexpr) &&  __cpp_constexpr-0 >= 201304
+    QVERIFY(verifyConstExpr<testRelaxedConstExpr()>(Qt::MiddleButton));
+#endif
 #endif
 }