diff --git a/src/network/access/qformdatabuilder.h b/src/network/access/qformdatabuilder.h
index 8c08214c398..4305ff8cb76 100644
--- a/src/network/access/qformdatabuilder.h
+++ b/src/network/access/qformdatabuilder.h
@@ -19,8 +19,6 @@
 QT_REQUIRE_CONFIG(http);
 #endif
 
-class tst_QFormDataBuilder;
-
 QT_BEGIN_NAMESPACE
 
 class QHttpPartPrivate;
@@ -75,7 +73,7 @@ private:
     Q_NETWORK_EXPORT QFormDataPartBuilder &setBodyHelper(const QByteArray &data,
                                                          QAnyStringView fileName,
                                                          QAnyStringView mimeType);
-    Q_NETWORK_EXPORT QHttpPart build();
+    QHttpPart build();
 
     QByteArray m_headerValue;
     QByteArray m_mimeType;
@@ -85,7 +83,6 @@ private:
     void *m_reserved = nullptr;
 
     friend class QFormDataBuilder;
-    friend class ::tst_QFormDataBuilder;
     friend void swap(QFormDataPartBuilder &lhs, QFormDataPartBuilder &rhs) noexcept
     { lhs.swap(rhs); }
 };
diff --git a/tests/auto/network/access/qformdatabuilder/tst_qformdatabuilder.cpp b/tests/auto/network/access/qformdatabuilder/tst_qformdatabuilder.cpp
index 65dd4fb2369..1502cb7e3c7 100644
--- a/tests/auto/network/access/qformdatabuilder/tst_qformdatabuilder.cpp
+++ b/tests/auto/network/access/qformdatabuilder/tst_qformdatabuilder.cpp
@@ -398,31 +398,31 @@ void tst_QFormDataBuilder::specifyMimeType()
 void tst_QFormDataBuilder::picksUtf8NameEncodingIfAsciiDoesNotSuffice_data()
 {
     QTest::addColumn<QAnyStringView>("name_data");
-    QTest::addColumn<QString>("expected_content_disposition_data");
+    QTest::addColumn<QByteArray>("expected_content_disposition_data");
 
-    QTest::newRow("latin1-ascii") << QAnyStringView("text"_L1) << uR"(form-data; name="text")"_s;
-    QTest::newRow("u8-ascii") << QAnyStringView(u8"text") << uR"(form-data; name="text")"_s;
-    QTest::newRow("u-ascii") << QAnyStringView(u"text") << uR"(form-data; name="text")"_s;
+    QTest::newRow("latin1-ascii") << QAnyStringView("text"_L1) << R"(form-data; name="text")"_ba;
+    QTest::newRow("u8-ascii") << QAnyStringView(u8"text") << R"(form-data; name="text")"_ba;
+    QTest::newRow("u-ascii") << QAnyStringView(u"text") << R"(form-data; name="text")"_ba;
 
     // 0xF6 is 'ö', use hex value with Latin-1 to avoid interpretation as UTF-8
-    QTest::newRow("latin1-latin") << QAnyStringView("t\xF6xt"_L1) << uR"(form-data; name="töxt")"_s;
-    QTest::newRow("u8-latin") << QAnyStringView(u8"töxt") << uR"(form-data; name="töxt")"_s;
-    QTest::newRow("u-latin") << QAnyStringView(u"töxt") << uR"(form-data; name="töxt")"_s;
+    QTest::newRow("latin1-latin") << QAnyStringView("t\xF6xt"_L1) << R"(form-data; name="töxt")"_ba;
+    QTest::newRow("u8-latin") << QAnyStringView(u8"töxt") << R"(form-data; name="töxt")"_ba;
+    QTest::newRow("u-latin") << QAnyStringView(u"töxt") << R"(form-data; name="töxt")"_ba;
 
-    QTest::newRow("u8-u8") << QAnyStringView(u8"テキスト") << uR"(form-data; name="テキスト")"_s;
+    QTest::newRow("u8-u8") << QAnyStringView(u8"テキスト") << R"(form-data; name="テキスト")"_ba;
 }
 
 void tst_QFormDataBuilder::picksUtf8NameEncodingIfAsciiDoesNotSuffice()
 {
     QFETCH(const QAnyStringView, name_data);
-    QFETCH(const QString, expected_content_disposition_data);
+    QFETCH(const QByteArray, expected_content_disposition_data);
 
-    QFormDataBuilder qfdb;
-    QFormDataPartBuilder &qfdpb = qfdb.part(name_data).setBody("some"_ba);
-    auto msg = QDebug::toString(qfdpb.build());
+    const auto msg = serialized([&](auto &builder) {
+            builder.part(name_data).setBody("some"_ba);
+        });
 
     QVERIFY2(msg.contains(expected_content_disposition_data),
-             qPrintable(u"content-disposition not found : "_s + expected_content_disposition_data));
+             "content-disposition not found : " + expected_content_disposition_data);
 }
 
 void tst_QFormDataBuilder::moveSemantics()