diff --git a/src/libslic3r/GCodeWriter.cpp b/src/libslic3r/GCodeWriter.cpp
index 5b428885b..ba857175a 100644
--- a/src/libslic3r/GCodeWriter.cpp
+++ b/src/libslic3r/GCodeWriter.cpp
@@ -353,12 +353,15 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
         the lift. */
     m_lifted = 0;
     m_pos = point;
-    
     std::ostringstream gcode;
     gcode << "G1 X" << XYZF_NUM(point.x())
-          <<   " Y" << XYZF_NUM(point.y())
-          <<   " Z" << XYZF_NUM(point.z())
-          <<   " F" << XYZF_NUM(this->config.travel_speed.value * 60.0);
+          << " Y" << XYZF_NUM(point.y());
+    if (config.z_step > SCALING_FACTOR)
+        gcode << " Z" << PRECISION(point.z(), 6);
+    else
+        gcode << " Z" << XYZF_NUM(point.z());
+    gcode <<   " F" << XYZF_NUM(this->config.travel_speed.value * 60.0);
+
     COMMENT(comment);
     gcode << "\n";
     return gcode.str();
@@ -388,8 +391,11 @@ std::string GCodeWriter::_travel_to_z(double z, const std::string &comment)
     m_pos.z() = z;
     
     std::ostringstream gcode;
-    gcode << "G1 Z" << XYZF_NUM(z)
-          <<   " F" << XYZF_NUM(this->config.travel_speed.value * 60.0);
+    if (config.z_step > SCALING_FACTOR)
+        gcode << "G1 Z" << PRECISION(z, 6);
+    else
+        gcode << "G1 Z" << XYZF_NUM(z);
+    gcode <<   " F" << XYZF_NUM(this->config.travel_speed.value * 60.0);
     COMMENT(comment);
     gcode << "\n";
     return gcode.str();
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 59c2b20de..590becf1a 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -2061,7 +2061,7 @@ void PrintConfigDef::init_fff_params()
     def->ratio_over = "perimeter_extrusion_width";
     def->min = 0;
     def->mode = comExpert;
-    def->set_default_value(new ConfigOptionFloatOrPercent(100, true));
+    def->set_default_value(new ConfigOptionFloatOrPercent(200, true));
 
     def = this->add("min_print_speed", coFloats);
     def->label = L("Min print speed");
@@ -3530,7 +3530,9 @@ void PrintConfigDef::init_fff_params()
     def = this->add("z_step", coFloat);
     def->label = L("Z full step");
     def->tooltip = L("Set this to the height moved when your Z motor (or equivalent) turns one step."
-                    "If your motor needs 200 steps to move your head/plater by 1mm, this field have to be 1/200 = 0.005");
+                    "If your motor needs 200 steps to move your head/plater by 1mm, this field have to be 1/200 = 0.005."
+                    "\nNote that the gcode will write the z values with 6 digits after the dot if z_step is set (it's 3 digits if it's disabled)."
+                    "\nPut 0 to disable.");
     def->cli = "z-step=f";
     def->sidetext = L("mm");
     def->min = 0.0001;
diff --git a/src/libslic3r/Slicing.cpp b/src/libslic3r/Slicing.cpp
index 444fdfc8e..7d99b6604 100644
--- a/src/libslic3r/Slicing.cpp
+++ b/src/libslic3r/Slicing.cpp
@@ -25,12 +25,14 @@ static const coordf_t MIN_LAYER_HEIGHT = 0.01;
 static const coordf_t MIN_LAYER_HEIGHT_DEFAULT = 0.07;
 // fields are with 8-number precision after the dot
 inline coordf_t check_z_step(const coordf_t val, const coordf_t z_step) {
+    if (z_step <= EPSILON) return val;
     uint64_t valint = uint64_t(val * 100000000. + 0.1);
     uint64_t stepint = uint64_t(z_step * 100000000. + 0.1);
     return (((valint + (stepint/2)) / stepint) * stepint) / 100000000.;
     //return int((val + z_step * 0.5) / z_step) * z_step;
 }
 inline bool test_z_step(const coordf_t val, const coordf_t z_step) {
+    if (z_step <= EPSILON) return val;
     uint64_t valint = uint64_t(val * 100000000. + 0.1);
     uint64_t stepint = uint64_t(z_step * 100000000. + 0.1);
     return valint % stepint == 0;
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index e0c77fd02..aabd10055 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -45,10 +45,13 @@ namespace GUI {
 wxDEFINE_EVENT(EVT_TAB_VALUE_CHANGED, wxCommandEvent);
 wxDEFINE_EVENT(EVT_TAB_PRESETS_CHANGED, SimpleEvent);
 
+//same as the slicing.cpp method, but it's easier to redefine it here
+// maybe i should have written it in the header.
 inline coordf_t check_z_step_temp(coordf_t val, coordf_t z_step) {
-    uint64_t valint = uint64_t(val * 100000. + 0.1);
-    uint64_t stepint = uint64_t(z_step * 100000. + 0.1);
-    return (((valint + (stepint / 2)) / stepint) * stepint) / 100000.;
+    if (z_step <= EPSILON) return val;
+    uint64_t valint = uint64_t(val * 100000000. + 0.1);
+    uint64_t stepint = uint64_t(z_step * 100000000. + 0.1);
+    return (((valint + (stepint / 2)) / stepint) * stepint) / 100000000.;
     //return int((val + z_step * 0.5) / z_step) * z_step;
 }