diff --git a/src/corelib/serialization/qjsondocument.cpp b/src/corelib/serialization/qjsondocument.cpp
index 338b752f139..642f058c722 100644
--- a/src/corelib/serialization/qjsondocument.cpp
+++ b/src/corelib/serialization/qjsondocument.cpp
@@ -450,18 +450,6 @@ QVariant QJsonDocument::toVariant() const
     return QJsonObject(container).toVariantMap();
 }
 
-/*!
- Converts the QJsonDocument to an indented, UTF-8 encoded JSON document.
-
- \sa fromJson()
- */
-#if !defined(QT_JSON_READONLY) || defined(Q_CLANG_QDOC)
-QByteArray QJsonDocument::toJson() const
-{
-    return toJson(Indented);
-}
-#endif
-
 /*!
     \enum QJsonDocument::JsonFormat
     \since 5.1
diff --git a/src/corelib/serialization/qjsondocument.h b/src/corelib/serialization/qjsondocument.h
index 8c2840eda7b..a09bd91601b 100644
--- a/src/corelib/serialization/qjsondocument.h
+++ b/src/corelib/serialization/qjsondocument.h
@@ -136,8 +136,7 @@ public:
     static QJsonDocument fromJson(const QByteArray &json, QJsonParseError *error = nullptr);
 
 #if !defined(QT_JSON_READONLY) || defined(Q_CLANG_QDOC)
-    QByteArray toJson() const; //### Merge in Qt6
-    QByteArray toJson(JsonFormat format) const;
+    QByteArray toJson(JsonFormat format = Indented) const;
 #endif
 
     bool isEmpty() const;
diff --git a/src/corelib/serialization/qjsonvalue.h b/src/corelib/serialization/qjsonvalue.h
index eb160f7f8fd..734493984c4 100644
--- a/src/corelib/serialization/qjsonvalue.h
+++ b/src/corelib/serialization/qjsonvalue.h
@@ -180,19 +180,13 @@ public:
     inline bool isObject() const { return type() == QJsonValue::Object; }
     inline bool isUndefined() const { return type() == QJsonValue::Undefined; }
 
-    inline bool toBool() const { return toValue().toBool(); }
-    inline int toInt() const { return toValue().toInt(); }
-    inline double toDouble() const { return toValue().toDouble(); }
-    inline QString toString() const { return toValue().toString(); }
+    inline bool toBool(bool defaultValue = false) const { return toValue().toBool(defaultValue); }
+    inline int toInt(int defaultValue = 0) const { return toValue().toInt(defaultValue); }
+    inline double toDouble(double defaultValue = 0) const { return toValue().toDouble(defaultValue); }
+    inline QString toString(const QString &defaultValue = {}) const { return toValue().toString(defaultValue); }
     QJsonArray toArray() const;
     QJsonObject toObject() const;
 
-    // ### Qt 6: Add default values
-    inline bool toBool(bool defaultValue) const { return toValue().toBool(defaultValue); }
-    inline int toInt(int defaultValue) const { return toValue().toInt(defaultValue); }
-    inline double toDouble(double defaultValue) const { return toValue().toDouble(defaultValue); }
-    inline QString toString(const QString &defaultValue) const { return toValue().toString(defaultValue); }
-
     inline bool operator==(const QJsonValue &other) const { return toValue() == other; }
     inline bool operator!=(const QJsonValue &other) const { return toValue() != other; }