diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index eee0e2533..4017b0e6b 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -211,7 +211,7 @@ sub retract {
     # reset extrusion distance during retracts
     # this makes sure we leave sufficient precision in the firmware
     if (!$Slic3r::use_relative_e_distances && $Slic3r::gcode_flavor ne 'mach3') {
-        $gcode .= "G92 " . $Slic3r::extrusion_axis . "0\n";
+        $gcode .= "G92 " . $Slic3r::extrusion_axis . "0\n" if $Slic3r::extrusion_axis;
         $self->extrusion_distance(0);
     }
     
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index f945f1305..5c6a59bea 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -746,7 +746,7 @@ sub export_gcode {
     print  $fh "G90 ; use absolute coordinates\n";
     print  $fh "G21 ; set units to millimeters\n";
     if ($Slic3r::gcode_flavor =~ /^(?:reprap|teacup)$/) {
-        printf $fh "G92 %s0 ; reset extrusion distance\n", $Slic3r::extrusion_axis;
+        printf $fh "G92 %s0 ; reset extrusion distance\n", $Slic3r::extrusion_axis if $Slic3r::extrusion_axis;
         if ($Slic3r::gcode_flavor =~ /^(?:reprap|makerbot)$/) {
             if ($Slic3r::use_relative_e_distances) {
                 print $fh "M83 ; use relative distances for extrusion\n";