diff --git a/src/slic3r/GUI/FirmwareDialog.cpp b/src/slic3r/GUI/FirmwareDialog.cpp
index 9e209faed..15a09aa71 100644
--- a/src/slic3r/GUI/FirmwareDialog.cpp
+++ b/src/slic3r/GUI/FirmwareDialog.cpp
@@ -107,7 +107,7 @@ struct FirmwareDialog::priv
 
 	// GUI elements
 	wxComboBox *port_picker;
-	wxStaticText *port_autodetect;
+	wxStaticText *txt_port_autodetect;
 	wxFilePickerCtrl *hex_picker;
 	wxStaticText *txt_status;
 	wxGauge *progressbar;
@@ -134,6 +134,7 @@ struct FirmwareDialog::priv
 	// Data
 	std::vector<SerialPortInfo> ports;
 	optional<SerialPortInfo> port;
+	bool port_autodetect;
 	HexFile hex_file;
 
 	// This is a shared pointer holding the background AvrDude task
@@ -150,6 +151,7 @@ struct FirmwareDialog::priv
 		btn_flash_label_flashing(_(L("Cancel"))),
 		label_status_flashing(_(L("Flashing in progress. Please do not disconnect the printer!"))),
 		timer_pulse(q),
+		port_autodetect(false),
 		progress_tasks_done(0),
 		progress_tasks_bar(0),
 		user_cancelled(false),
@@ -161,7 +163,7 @@ struct FirmwareDialog::priv
 	void set_txt_status(const wxString &label);
 	void flashing_start(unsigned tasks);
 	void flashing_done(AvrDudeComplete complete);
-	void enable_port_picker(bool enable);
+	void set_autodetect(bool autodetect);
 	void update_flash_enabled();
 	void load_hex_file(const wxString &path);
 	void queue_event(AvrdudeEvent aevt, wxString message);
@@ -216,8 +218,10 @@ void FirmwareDialog::priv::find_serial_ports()
 					idx = i;
 					break;
 				}
-			if (idx != -1)
+			if (idx != -1) {
 				port_picker->SetSelection(idx);
+				update_flash_enabled();
+			}
 		}
 	}
 }
@@ -282,11 +286,13 @@ void FirmwareDialog::priv::flashing_done(AvrDudeComplete complete)
 	}
 }
 
-void FirmwareDialog::priv::enable_port_picker(bool enable)
+void FirmwareDialog::priv::set_autodetect(bool autodetect)
 {
-	port_picker->Show(enable);
-	btn_rescan->Show(enable);
-	port_autodetect->Show(! enable);
+	port_autodetect = autodetect;
+
+	port_picker->Show(!autodetect);
+	btn_rescan->Show(!autodetect);
+	txt_port_autodetect->Show(autodetect);
 	q->Layout();
 	fit_no_shrink();
 }
@@ -294,7 +300,7 @@ void FirmwareDialog::priv::enable_port_picker(bool enable)
 void FirmwareDialog::priv::update_flash_enabled()
 {
 	const bool hex_exists = wxFileExists(hex_picker->GetPath());
-	const bool port_valid = get_serial_port();
+	const bool port_valid = port_autodetect || get_serial_port();
 
 	btn_flash->Enable(hex_exists && port_valid);
 }
@@ -302,8 +308,8 @@ void FirmwareDialog::priv::update_flash_enabled()
 void FirmwareDialog::priv::load_hex_file(const wxString &path)
 {
 	hex_file = HexFile(path.wx_str());
-	const bool auto_lookup = hex_file.device == HexFile::DEV_MM_CONTROL || hex_file.device == HexFile::DEV_CW1;
-	enable_port_picker(! auto_lookup);
+	const bool autodetect = hex_file.device == HexFile::DEV_MM_CONTROL || hex_file.device == HexFile::DEV_CW1;
+	set_autodetect(autodetect);
 }
 
 void FirmwareDialog::priv::queue_event(AvrdudeEvent aevt, wxString message)
@@ -598,7 +604,7 @@ void FirmwareDialog::priv::perform_upload()
 
 	load_hex_file(filename);  // Might already be loaded, but we want to make sure it's fresh
 
-	if (! get_serial_port()) {
+	if (!port_autodetect && !get_serial_port()) {
 		return;
 	}
 
@@ -801,13 +807,13 @@ FirmwareDialog::FirmwareDialog(wxWindow *parent) :
 
 	auto *label_port_picker = new wxStaticText(panel, wxID_ANY, _(L("Serial port:")));
 	p->port_picker = new wxComboBox(panel, wxID_ANY);
-	p->port_autodetect = new wxStaticText(panel, wxID_ANY, _(L("Autodetected")));
+	p->txt_port_autodetect = new wxStaticText(panel, wxID_ANY, _(L("Autodetected")));
 	p->btn_rescan = new wxButton(panel, wxID_ANY, _(L("Rescan")));
 	auto *port_sizer = new wxBoxSizer(wxHORIZONTAL);
 	port_sizer->Add(p->port_picker, 1, wxEXPAND | wxRIGHT, SPACING);
 	port_sizer->Add(p->btn_rescan, 0);
-	port_sizer->Add(p->port_autodetect, 1, wxEXPAND);
-	p->enable_port_picker(true);
+	port_sizer->Add(p->txt_port_autodetect, 1, wxEXPAND);
+	p->set_autodetect(false);
 
 	auto *label_progress = new wxStaticText(panel, wxID_ANY, _(L("Progress:")));
 	p->progressbar = new wxGauge(panel, wxID_ANY, 1, wxDefaultPosition, wxDefaultSize, wxGA_HORIZONTAL | wxGA_SMOOTH);