diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index a1310992f43..ebe79e0232f 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -948,6 +948,12 @@ void QMetaType::unregisterMetaType(QMetaType type)
     than the QMetaType \a b, otherwise returns \c false.
 */
 
+/*! \internal */
+bool QMetaTypeModuleHelper::convert(const void *, int, void *, int) const
+{
+    return false;
+}
+
 #define QT_ADD_STATIC_METATYPE(MetaTypeName, MetaTypeId, RealName) \
     { #RealName, sizeof(#RealName) - 1, MetaTypeId },
 
diff --git a/src/corelib/kernel/qmetatype_p.h b/src/corelib/kernel/qmetatype_p.h
index 71a225d5e6e..7e0457771f0 100644
--- a/src/corelib/kernel/qmetatype_p.h
+++ b/src/corelib/kernel/qmetatype_p.h
@@ -38,20 +38,21 @@ QT_BEGIN_NAMESPACE
             assign_and_return \
         }
 
-class QMetaTypeModuleHelper
+class Q_CORE_EXPORT QMetaTypeModuleHelper
 {
     Q_DISABLE_COPY_MOVE(QMetaTypeModuleHelper)
 protected:
     QMetaTypeModuleHelper() = default;
     ~QMetaTypeModuleHelper() = default;
 public:
+    Q_WEAK_OVERLOAD // prevent it from entering the ABI and rendering constexpr useless
     static constexpr auto makePair(int from, int to) -> quint64
     {
         return (quint64(from) << 32) + quint64(to);
     }
 
     virtual const QtPrivate::QMetaTypeInterface *interfaceForType(int) const = 0;
-    virtual bool convert(const void *, int, void *, int) const { return false; }
+    virtual bool convert(const void *, int, void *, int) const;
 };
 
 extern Q_CORE_EXPORT const QMetaTypeModuleHelper *qMetaTypeGuiHelper;