diff --git a/src/corelib/kernel/qjniarray.h b/src/corelib/kernel/qjniarray.h
index 8bf313db735..cd85ae48043 100644
--- a/src/corelib/kernel/qjniarray.h
+++ b/src/corelib/kernel/qjniarray.h
@@ -735,9 +735,7 @@ public:
         } else if constexpr (std::is_same_v<QString, T>) {
             jstring string = static_cast<jstring>(env->GetObjectArrayElement(arrayObject(), i));
             if (string) {
-                const auto length = env->GetStringLength(string);
-                QString res(length, Qt::Uninitialized);
-                env->GetStringRegion(string, 0, length, reinterpret_cast<jchar *>(res.data()));
+                QString res = QtJniTypes::Detail::toQString(string, env);
                 env->DeleteLocalRef(string);
                 return res;
             } else {
@@ -817,6 +815,8 @@ public:
             for (auto element : *this) {
                 if constexpr (std::is_same_v<decltype(element), QString>)
                     container.emplace_back(element);
+                else if constexpr (std::is_same_v<decltype(element), jstring>)
+                    container.emplace_back(QtJniTypes::Detail::toQString(element, env));
                 else
                     container.emplace_back(QJniObject(element).toString());
             }
diff --git a/src/corelib/kernel/qjniobject.cpp b/src/corelib/kernel/qjniobject.cpp
index 2a3c365a0e7..b780d0e55b7 100644
--- a/src/corelib/kernel/qjniobject.cpp
+++ b/src/corelib/kernel/qjniobject.cpp
@@ -1325,8 +1325,7 @@ QJniObject QJniObject::getObjectField(const char *fieldName, const char *signatu
 QJniObject QJniObject::fromString(const QString &string)
 {
     QJniEnvironment env;
-    jstring stringRef = env->NewString(reinterpret_cast<const jchar*>(string.constData()),
-                                                                      string.length());
+    jstring stringRef = QtJniTypes::Detail::fromQString(string, env.jniEnv());
     QJniObject stringObject = getCleanJniObject(stringRef, env.jniEnv());
     stringObject.d->m_className = "java/lang/String";
     return stringObject;
@@ -1352,10 +1351,7 @@ QString QJniObject::toString() const
         return QString();
 
     QJniObject string = callObjectMethod<jstring>("toString");
-    const int strLength = string.jniEnv()->GetStringLength(string.object<jstring>());
-    QString res(strLength, Qt::Uninitialized);
-    string.jniEnv()->GetStringRegion(string.object<jstring>(), 0, strLength, reinterpret_cast<jchar *>(res.data()));
-    return res;
+    return QtJniTypes::Detail::toQString(string.object<jstring>(), string.jniEnv());
 }
 
 /*!
diff --git a/src/corelib/kernel/qjniobject.h b/src/corelib/kernel/qjniobject.h
index 76f1c0787ec..e59773f8a77 100644
--- a/src/corelib/kernel/qjniobject.h
+++ b/src/corelib/kernel/qjniobject.h
@@ -31,21 +31,21 @@ class Q_CORE_EXPORT QJniObject
             if (hasFrame)
                 env->PopLocalFrame(nullptr);
         }
+        bool ensureFrame()
+        {
+            if (!hasFrame)
+                hasFrame = jniEnv()->PushLocalFrame(sizeof...(Args)) == 0;
+            return hasFrame;
+        }
         template <typename T>
         auto newLocalRef(jobject object)
         {
-            if (!hasFrame) {
-                if (jniEnv()->PushLocalFrame(sizeof...(Args)) < 0)
-                    return T{}; // JVM is out of memory, avoid making matters worse
-                hasFrame = true;
+            if (!ensureFrame()) {
+                // if the JVM is out of memory, avoid making matters worse
+                return T{};
             }
             return static_cast<T>(jniEnv()->NewLocalRef(object));
         }
-        template <typename T>
-        auto newLocalRef(const QJniObject &object)
-        {
-            return newLocalRef<T>(object.template object<T>());
-        }
         JNIEnv *jniEnv() const
         {
             if (!env)
@@ -870,7 +870,9 @@ auto QJniObject::LocalFrame<Args...>::convertToJni(T &&value)
 {
     using Type = q20::remove_cvref_t<T>;
     if constexpr (std::is_same_v<Type, QString>) {
-        return newLocalRef<jstring>(QJniObject::fromString(value));
+        if (ensureFrame()) // fromQString already returns a local reference
+            return QtJniTypes::Detail::fromQString(value, jniEnv());
+        return jstring{};
     } else if constexpr (QtJniTypes::IsJniArray<Type>::value) {
         return value.arrayObject();
     } else if constexpr (QtJniTypes::detail::isCompatibleSourceContainer<T>) {
diff --git a/src/corelib/kernel/qjnitypes.h b/src/corelib/kernel/qjnitypes.h
index d717c0c0d25..37b0bde2bd2 100644
--- a/src/corelib/kernel/qjnitypes.h
+++ b/src/corelib/kernel/qjnitypes.h
@@ -163,7 +163,7 @@ struct JNITypeForArgImpl<QString>
 
     static QString fromVarArg(Type t)
     {
-        return QJniObject(t).toString();
+        return QtJniTypes::Detail::toQString(t, QJniEnvironment::getJniEnv());
     }
 };
 
diff --git a/src/corelib/kernel/qjnitypes_impl.h b/src/corelib/kernel/qjnitypes_impl.h
index d9635090238..6324ace17de 100644
--- a/src/corelib/kernel/qjnitypes_impl.h
+++ b/src/corelib/kernel/qjnitypes_impl.h
@@ -4,7 +4,7 @@
 #ifndef QJNITYPES_IMPL_H
 #define QJNITYPES_IMPL_H
 
-#include <QtCore/qglobal.h>
+#include <QtCore/qstring.h>
 #include <QtCore/q20type_traits.h>
 
 #if defined(Q_QDOC) || defined(Q_OS_ANDROID)
@@ -15,6 +15,22 @@ QT_BEGIN_NAMESPACE
 namespace QtJniTypes
 {
 
+namespace Detail
+{
+static inline jstring fromQString(const QString &string, JNIEnv *env)
+{
+    return env->NewString(reinterpret_cast<const jchar*>(string.constData()), string.length());
+}
+
+static inline QString toQString(jstring string, JNIEnv *env)
+{
+    const jsize length = env->GetStringLength(string);
+    QString res(length, Qt::Uninitialized);
+    env->GetStringRegion(string, 0, length, reinterpret_cast<jchar *>(res.data()));
+    return res;
+}
+} // namespace Detail
+
 // a constexpr type for string literals of any character width, aware of the length
 // of the string.
 template<size_t N_WITH_NULL, typename BaseType = char>