diff --git a/lib/Slic3r/GUI/Controller/PrinterPanel.pm b/lib/Slic3r/GUI/Controller/PrinterPanel.pm
index 6a28e2ace..9e2dc211d 100644
--- a/lib/Slic3r/GUI/Controller/PrinterPanel.pm
+++ b/lib/Slic3r/GUI/Controller/PrinterPanel.pm
@@ -126,7 +126,7 @@ sub new {
         my $serial_speed_sizer = Wx::BoxSizer->new(wxHORIZONTAL);
         {
             $self->{serial_speed_combobox} = Wx::ComboBox->new($self, -1, $config->serial_speed, wxDefaultPosition, wxDefaultSize,
-                ["115200", "250000"]);
+                ["57600", "115200", "250000"]);
             $self->{serial_speed_combobox}->SetFont($Slic3r::GUI::small_font);
             $serial_speed_sizer->Add($self->{serial_speed_combobox}, 0, wxALIGN_CENTER_VERTICAL, 0);
         }
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index 4d886893f..d6589da13 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -238,7 +238,7 @@ sub new {
     EVT_LEFT_UP($self->{btn_send_gcode}, sub {
         my (undef, $e) = @_;
         
-        my $alt = $e->AltDown;
+        my $alt = $e->ShiftDown;
         wxTheApp->CallAfter(sub {
             $self->prepare_send($alt);
         });
diff --git a/xs/src/libslic3r/GCodeSender.cpp b/xs/src/libslic3r/GCodeSender.cpp
index bb91a84c1..c880ee408 100644
--- a/xs/src/libslic3r/GCodeSender.cpp
+++ b/xs/src/libslic3r/GCodeSender.cpp
@@ -355,6 +355,7 @@ GCodeSender::on_read(const boost::system::error_code& error,
             // extract the first number from line
             boost::algorithm::trim_left_if(line, !boost::algorithm::is_digit());
             size_t toresend = boost::lexical_cast<size_t>(line.substr(0, line.find_first_not_of("0123456789")));
+            toresend++; // N is 0-based
             if (toresend >= this->sent - this->last_sent.size()) {
                 {
                     boost::lock_guard<boost::mutex> l(this->queue_mutex);
@@ -473,8 +474,8 @@ GCodeSender::do_send()
     if (line.empty()) return;
     
     // compute full line
-    this->sent++;
     std::string full_line = "N" + boost::lexical_cast<std::string>(this->sent) + " " + line;
+    this->sent++;
     
     // calculate checksum
     int cs = 0;
diff --git a/xs/src/libslic3r/PrintConfig.cpp b/xs/src/libslic3r/PrintConfig.cpp
index 4bd2bc8b6..c9fb48318 100644
--- a/xs/src/libslic3r/PrintConfig.cpp
+++ b/xs/src/libslic3r/PrintConfig.cpp
@@ -1108,6 +1108,7 @@ PrintConfigDef::PrintConfigDef()
     def->cli = "serial-speed=i";
     def->min = 1;
     def->max = 300000;
+    def->enum_values.push_back("57600");
     def->enum_values.push_back("115200");
     def->enum_values.push_back("250000");
     def->default_value = new ConfigOptionInt(250000);