diff --git a/src/corelib/global/qflags.h b/src/corelib/global/qflags.h
index 0ec7f4383f5..05225b98d23 100644
--- a/src/corelib/global/qflags.h
+++ b/src/corelib/global/qflags.h
@@ -12,7 +12,6 @@
 
 QT_BEGIN_NAMESPACE
 
-class QDataStream;
 template<typename Enum> class QFlags;
 
 class QFlag
@@ -206,10 +205,6 @@ private:
         return (it == end ? Int(0) : (Int(*it) | initializer_list_helper(it + 1, end)));
     }
 
-#ifndef QT_NO_DATASTREAM
-    template <typename E> friend QDataStream &operator<<(QDataStream &, QFlags<E>);
-    template <typename E> friend QDataStream &operator>>(QDataStream &, QFlags<E> &);
-#endif
     using Base::i;
 };
 
diff --git a/src/corelib/serialization/qdatastream.h b/src/corelib/serialization/qdatastream.h
index 264454e9b6a..d03070b9195 100644
--- a/src/corelib/serialization/qdatastream.h
+++ b/src/corelib/serialization/qdatastream.h
@@ -517,11 +517,16 @@ inline QDataStream &QDataStream::operator<<(quint64 i)
 
 template <typename Enum>
 inline QDataStream &operator<<(QDataStream &s, QFlags<Enum> e)
-{ return s << e.i; }
+{ return s << e.toInt(); }
 
 template <typename Enum>
 inline QDataStream &operator>>(QDataStream &s, QFlags<Enum> &e)
-{ return s >> e.i; }
+{
+    typename QFlags<Enum>::Int i;
+    s >> i;
+    e = QFlags<Enum>::fromInt(i);
+    return s;
+}
 
 template <typename T>
 typename std::enable_if_t<std::is_enum<T>::value, QDataStream &>
diff --git a/src/corelib/text/qchar.h b/src/corelib/text/qchar.h
index fb6f3136a59..c090da824ef 100644
--- a/src/corelib/text/qchar.h
+++ b/src/corelib/text/qchar.h
@@ -11,7 +11,7 @@
 
 QT_BEGIN_NAMESPACE
 
-
+class QDataStream;
 class QString;
 
 struct QLatin1Char
diff --git a/src/corelib/tools/qline.h b/src/corelib/tools/qline.h
index 03dac30e162..b8523788cf2 100644
--- a/src/corelib/tools/qline.h
+++ b/src/corelib/tools/qline.h
@@ -8,6 +8,7 @@
 
 QT_BEGIN_NAMESPACE
 
+class QDataStream;
 class QLineF;
 
 /*******************************************************************************
diff --git a/src/corelib/tools/qmargins.h b/src/corelib/tools/qmargins.h
index 3b29860d663..8782b147afc 100644
--- a/src/corelib/tools/qmargins.h
+++ b/src/corelib/tools/qmargins.h
@@ -14,6 +14,7 @@ QT_BEGIN_NAMESPACE
 
 QT_ENABLE_P0846_SEMANTICS_FOR(get)
 
+class QDataStream;
 class QMarginsF;
 
 /*****************************************************************************
diff --git a/src/corelib/tools/qpoint.h b/src/corelib/tools/qpoint.h
index 50b4c864be8..d9a0fa53235 100644
--- a/src/corelib/tools/qpoint.h
+++ b/src/corelib/tools/qpoint.h
@@ -19,6 +19,7 @@ QT_BEGIN_NAMESPACE
 
 QT_ENABLE_P0846_SEMANTICS_FOR(get)
 
+class QDataStream;
 class QPointF;
 
 class QPoint