diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index d2ae580d9d8..fd8a164f07e 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -1206,8 +1206,7 @@ std::vector<GCode::LayerToPrint> GCode::collect_layers_to_print(const PrintObjec
             // Allow empty support layers, as the support generator may produce no extrusions for non-empty support regions.
             || (layer_to_print.support_layer /* && layer_to_print.support_layer->has_extrusions() */)) {
             double top_cd = object.config().support_top_z_distance;
-            //double bottom_cd = object.config().support_bottom_z_distance == 0. ? top_cd : object.config().support_bottom_z_distance;
-            double bottom_cd = top_cd;
+            double bottom_cd = object.config().support_bottom_z_distance;
 
             double extra_gap = (layer_to_print.support_layer ? bottom_cd : top_cd);
 
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 2702e3b47f2..94cb997fbcc 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -3501,6 +3501,7 @@ def = this->add("filament_loading_speed", coFloats);
     def = this->add("support_top_z_distance", coFloat);
     //def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->label = L("Top Z distance");
+    def->min = 0;
     def->category = L("Support");
     def->tooltip = L("The z gap between the top support interface and object");
     def->sidetext = L("mm");
@@ -3516,12 +3517,12 @@ def = this->add("filament_loading_speed", coFloats);
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(0.2));
 
-    // BBS:MusangKing
     def = this->add("support_bottom_z_distance", coFloat);
     def->label = L("Bottom Z distance");
     def->category = L("Support");
     def->tooltip = L("The z gap between the bottom support interface and object");
     def->sidetext = L("mm");
+    def->min = 0;
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(0.2));
 
diff --git a/src/libslic3r/Slicing.cpp b/src/libslic3r/Slicing.cpp
index acfb17e856b..989610c7ac0 100644
--- a/src/libslic3r/Slicing.cpp
+++ b/src/libslic3r/Slicing.cpp
@@ -119,8 +119,6 @@ SlicingParameters SlicingParameters::create_from_config(
         //BBS
         params.gap_object_support = object_config.support_bottom_z_distance.value; 
         params.gap_support_object = object_config.support_top_z_distance.value;
-        if (params.gap_object_support <= 0)
-            params.gap_object_support = params.gap_support_object;
 
         if (!print_config.independent_support_layer_height) {
             params.gap_raft_object = std::round(params.gap_raft_object / object_config.layer_height + EPSILON) * object_config.layer_height;