diff --git a/src/platform/qt/ForwarderController.cpp b/src/platform/qt/ForwarderController.cpp
index 6083a1d5e..fe0530a73 100644
--- a/src/platform/qt/ForwarderController.cpp
+++ b/src/platform/qt/ForwarderController.cpp
@@ -65,7 +65,11 @@ void ForwarderController::startBuild(const QString& outFilename) {
 			return;
 		}
 	}
-	downloadManifest();
+	if (m_baseFilename.isEmpty()) {
+		downloadManifest();
+	} else {
+		m_generator->rebuild(m_baseFilename, m_outFilename);
+	}
 }
 
 void ForwarderController::downloadForwarderKit() {
@@ -201,7 +205,9 @@ void ForwarderController::gotBuild(QNetworkReply* reply) {
 }
 
 void ForwarderController::cleanup() {
-	m_sourceFile.remove();
+	if (m_sourceFile.exists()) {
+		m_sourceFile.remove();
+	}
 	m_inProgress = false;
 
 #if defined(Q_OS_WIN) || defined(Q_OS_MAC)
diff --git a/src/platform/qt/ForwarderController.h b/src/platform/qt/ForwarderController.h
index 7129b63d0..e53006bc2 100644
--- a/src/platform/qt/ForwarderController.h
+++ b/src/platform/qt/ForwarderController.h
@@ -30,6 +30,10 @@ public:
 	void setGenerator(std::unique_ptr<ForwarderGenerator>&& generator);
 	ForwarderGenerator* generator() { return m_generator.get(); }
 
+	void setBaseFilename(const QString& path) { m_baseFilename = path; }
+	void clearBaseFilename() { m_baseFilename = QString(); }
+	QString baseFilename() const { return m_baseFilename; }
+
 	QString channel() const { return m_channel; }
 	bool inProgress() const { return m_inProgress; }
 
@@ -62,6 +66,7 @@ private:
 	QString m_outFilename;
 	std::unique_ptr<ForwarderGenerator> m_generator;
 	QFile m_sourceFile;
+	QString m_baseFilename;
 	bool m_inProgress = false;
 	QByteArray m_originalPath;
 };
diff --git a/src/platform/qt/ForwarderView.cpp b/src/platform/qt/ForwarderView.cpp
index 2e8929f1d..0546e7180 100644
--- a/src/platform/qt/ForwarderView.cpp
+++ b/src/platform/qt/ForwarderView.cpp
@@ -94,6 +94,11 @@ void ForwarderView::build() {
 	}
 	m_controller.generator()->setTitle(m_ui.title->text());
 	m_controller.generator()->setRom(m_ui.romFilename->text());
+	if (m_ui.baseType->currentIndex() == 2) {
+		m_controller.setBaseFilename(m_ui.baseFilename->text());
+	} else {
+		m_controller.clearBaseFilename();		
+	}
 	m_controller.startBuild(m_ui.outputFilename->text());
 	m_ui.buttonBox->button(QDialogButtonBox::Ok)->setEnabled(false);
 	m_ui.progressBar->setEnabled(true);
@@ -120,9 +125,21 @@ void ForwarderView::validate() {
 	if (!m_ui.system->checkedButton()) {
 		valid = false;
 	}
-	if (m_ui.baseType->currentIndex() != 1) {
+	if (m_ui.baseType->currentIndex() < 1) {
 		valid = false;
 	}
+	if (m_ui.baseType->currentIndex() == 2) {
+		m_ui.baseFilename->setEnabled(true);
+		m_ui.baseLabel->setEnabled(true);
+		m_ui.baseBrowse->setEnabled(true);
+		if (m_ui.baseFilename->text().isEmpty()) {
+			valid = false;
+		}
+	} else {
+		m_ui.baseFilename->setEnabled(true);
+		m_ui.baseLabel->setEnabled(true);
+		m_ui.baseBrowse->setEnabled(true);
+	}
 	if (m_controller.inProgress()) {
 		valid = false;
 	}
diff --git a/src/platform/qt/ForwarderView.ui b/src/platform/qt/ForwarderView.ui
index d5a7de842..1c72e3caa 100644
--- a/src/platform/qt/ForwarderView.ui
+++ b/src/platform/qt/ForwarderView.ui
@@ -87,7 +87,7 @@
        </widget>
       </item>
       <item row="6" column="0">
-       <widget class="QLabel" name="label_6">
+       <widget class="QLabel" name="baseLabel">
         <property name="enabled">
          <bool>false</bool>
         </property>