diff --git a/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache b/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
index c4655177968..7fb010be106 100644
--- a/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
@@ -656,9 +656,15 @@ void {{classname}}::{{nickname}}({{#allParams}}{{#required}}const {{{dataType}}}
         }
     }
 {{/cookieParams}}
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &{{prefix}}HttpRequestWorker::on_execution_finished, this, &{{classname}}::{{nickname}}Callback);
     connect(this, &{{classname}}::abortRequestsSignal, worker, &QObject::deleteLater);
diff --git a/samples/client/petstore/cpp-qt/client/PFXPetApi.cpp b/samples/client/petstore/cpp-qt/client/PFXPetApi.cpp
index 8dd0658865d..a17deb8dfac 100644
--- a/samples/client/petstore/cpp-qt/client/PFXPetApi.cpp
+++ b/samples/client/petstore/cpp-qt/client/PFXPetApi.cpp
@@ -233,9 +233,15 @@ void PFXPetApi::addPet(const PFXPet &body) {
         QByteArray output = body.asJson().toUtf8();
         input.request_body.append(output);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::addPetCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -295,9 +301,15 @@ void PFXPetApi::deletePet(const qint64 &pet_id, const ::test_namespace::Optional
             input.headers.insert("api_key", ::test_namespace::toStringValue(api_key.value()));
         }
         }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::deletePetCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -423,9 +435,15 @@ void PFXPetApi::findPetsByStatus(const QList<QString> &status) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::findPetsByStatusCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -561,9 +579,15 @@ void PFXPetApi::findPetsByTags(const QList<QString> &tags) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::findPetsByTagsCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -631,9 +655,15 @@ void PFXPetApi::getPetById(const qint64 &pet_id) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::getPetByIdCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -678,9 +708,15 @@ void PFXPetApi::updatePet(const PFXPet &body) {
         QByteArray output = body.asJson().toUtf8();
         input.request_body.append(output);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::updatePetCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -742,9 +778,15 @@ void PFXPetApi::updatePetWithForm(const qint64 &pet_id, const ::test_namespace::
         input.add_var("status", ::test_namespace::toStringValue(status.value()));
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::updatePetWithFormCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -806,9 +848,15 @@ void PFXPetApi::uploadFile(const qint64 &pet_id, const ::test_namespace::Optiona
         input.add_file("file", file.value().local_filename, file.value().request_filename, file.value().mime_type);
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXPetApi::uploadFileCallback);
     connect(this, &PFXPetApi::abortRequestsSignal, worker, &QObject::deleteLater);
diff --git a/samples/client/petstore/cpp-qt/client/PFXStoreApi.cpp b/samples/client/petstore/cpp-qt/client/PFXStoreApi.cpp
index 5766052aafd..e0e9cc9281b 100644
--- a/samples/client/petstore/cpp-qt/client/PFXStoreApi.cpp
+++ b/samples/client/petstore/cpp-qt/client/PFXStoreApi.cpp
@@ -235,9 +235,15 @@ void PFXStoreApi::deleteOrder(const QString &order_id) {
     PFXHttpRequestInput input(fullPath, "DELETE");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXStoreApi::deleteOrderCallback);
     connect(this, &PFXStoreApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -281,9 +287,15 @@ void PFXStoreApi::getInventory() {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXStoreApi::getInventoryCallback);
     connect(this, &PFXStoreApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -347,9 +359,15 @@ void PFXStoreApi::getOrderById(const qint64 &order_id) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXStoreApi::getOrderByIdCallback);
     connect(this, &PFXStoreApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -394,9 +412,15 @@ void PFXStoreApi::placeOrder(const PFXOrder &body) {
         QByteArray output = body.asJson().toUtf8();
         input.request_body.append(output);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXStoreApi::placeOrderCallback);
     connect(this, &PFXStoreApi::abortRequestsSignal, worker, &QObject::deleteLater);
diff --git a/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp b/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
index dd42999d701..cc38ec0bb08 100644
--- a/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
+++ b/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
@@ -233,9 +233,15 @@ void PFXUserApi::createUser(const PFXUser &body) {
         QByteArray output = body.asJson().toUtf8();
         input.request_body.append(output);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::createUserCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -279,9 +285,15 @@ void PFXUserApi::createUsersWithArrayInput(const QList<PFXUser> &body) {
         QByteArray bytes = doc.toJson();
         input.request_body.append(bytes);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::createUsersWithArrayInputCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -325,9 +337,15 @@ void PFXUserApi::createUsersWithListInput(const QList<PFXUser> &body) {
         QByteArray bytes = doc.toJson();
         input.request_body.append(bytes);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::createUsersWithListInputCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -381,9 +399,15 @@ void PFXUserApi::deleteUser(const QString &username) {
     PFXHttpRequestInput input(fullPath, "DELETE");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::deleteUserCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -437,9 +461,15 @@ void PFXUserApi::getUserByName(const QString &username) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::getUserByNameCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -511,9 +541,15 @@ void PFXUserApi::loginUser(const QString &username, const QString &password) {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::loginUserCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -555,9 +591,15 @@ void PFXUserApi::logoutUser() {
     PFXHttpRequestInput input(fullPath, "GET");
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::logoutUserCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);
@@ -615,9 +657,15 @@ void PFXUserApi::updateUser(const QString &username, const PFXUser &body) {
         QByteArray output = body.asJson().toUtf8();
         input.request_body.append(output);
     }
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     for (auto keyValueIt = _defaultHeaders.keyValueBegin(); keyValueIt != _defaultHeaders.keyValueEnd(); keyValueIt++) {
         input.headers.insert(keyValueIt->first, keyValueIt->second);
     }
+#else
+    for (auto key = _defaultHeaders.keys()) {
+        input.headers.insert(key, _defaultHeaders[key]);
+    }
+#endif
 
     connect(worker, &PFXHttpRequestWorker::on_execution_finished, this, &PFXUserApi::updateUserCallback);
     connect(this, &PFXUserApi::abortRequestsSignal, worker, &QObject::deleteLater);