diff --git a/src/libnest2d/include/libnest2d/nester.hpp b/src/libnest2d/include/libnest2d/nester.hpp
index db6cc050a..2ac0392d7 100644
--- a/src/libnest2d/include/libnest2d/nester.hpp
+++ b/src/libnest2d/include/libnest2d/nester.hpp
@@ -75,7 +75,7 @@ class _Item {
 
 public:
     int itemid_{ 0 };
-    int extrude_id{ 1 };
+    std::vector<int> extrude_ids;
     double height{ 0 };
     double print_temp{ 0 };
     double bed_temp{ 0 };
diff --git a/src/libnest2d/include/libnest2d/selections/firstfit.hpp b/src/libnest2d/include/libnest2d/selections/firstfit.hpp
index bc2b5a96b..e739a8870 100644
--- a/src/libnest2d/include/libnest2d/selections/firstfit.hpp
+++ b/src/libnest2d/include/libnest2d/selections/firstfit.hpp
@@ -114,13 +114,14 @@ public:
             double score = LARGE_COST_TO_REJECT+1, best_score = LARGE_COST_TO_REJECT+1;
             double score_all_plates = 0, score_all_plates_best = std::numeric_limits<double>::max();
             typename Placer::PackResult result, result_best, result_firstfit;
-            size_t j = 0;
+            int j = 0;
             while(!was_packed && !cancelled()) {
                 for(; j < placers.size() && !was_packed && !cancelled(); j++) {
                     result = placers[j].pack(*it, rem(it, store_));
                     score = result.score();
                     score_all_plates = std::accumulate(placers.begin(), placers.begin() + j, score,
                         [](double sum, const Placer& elem) { return sum + elem.score(); });
+                    if (this->unfitindicator_) this->unfitindicator_(it->get().name + " bed_id="+std::to_string(j) + ",score=" + std::to_string(score));
 
                     if(score >= 0 && score < LARGE_COST_TO_REJECT) {
                         if (bed_id_firstfit == -1) {
diff --git a/src/libslic3r/Arrange.cpp b/src/libslic3r/Arrange.cpp
index 83c803b3c..2eb90dfe6 100644
--- a/src/libslic3r/Arrange.cpp
+++ b/src/libslic3r/Arrange.cpp
@@ -452,20 +452,25 @@ protected:
         }
 
         std::set<int> extruder_ids;
+        int           non_virt_cnt = 0;
         for (int i = 0; i < m_items.size(); i++) {
             Item& p = m_items[i];
             if (p.is_virt_object) continue;
-            extruder_ids.insert(p.extrude_id);
-            // add a large cost if not multi materials on same plate is not allowed 
-            if (!params.allow_multi_materials_on_same_plate)
-                score += LARGE_COST_TO_REJECT * (item.extrude_id != p.extrude_id);
+            extruder_ids.insert(p.extrude_ids.begin(),p.extrude_ids.end());
+            non_virt_cnt++;
         }
+        extruder_ids.insert(item.extrude_ids.begin(),item.extrude_ids.end());
 
+        // add a large cost if not multi materials on same plate is not allowed
+        if (!params.allow_multi_materials_on_same_plate) {
+            // non_virt_cnt==0 means it's the first object, which can be multi-color
+            if (extruder_ids.size() > 1 && non_virt_cnt > 0)
+                score += LARGE_COST_TO_REJECT * 1.1;
+        }
         // for layered printing, we want extruder change as few as possible
         // this has very weak effect, CAN NOT use a large weight
         if (!params.is_seq_print) {
-            extruder_ids.insert(item.extrude_id);
-            score += 1 * std::max(0, ((int)extruder_ids.size() - 1));
+            score += 1 * std::max(0, ((int) extruder_ids.size() - 1));
         }
 
         return std::make_tuple(score, fullbb);
@@ -601,7 +606,7 @@ public:
             }
             else {
                 return i1.bed_temp != i2.bed_temp ? (i1.bed_temp > i2.bed_temp) :
-                    (i1.extrude_id != i2.extrude_id ? (i1.extrude_id < i2.extrude_id) : (i1.area() > i2.area()));
+                    (i1.extrude_ids != i2.extrude_ids ? (i1.extrude_ids.front() < i2.extrude_ids.front()) : (i1.area() > i2.area()));
             }
         };
         
@@ -850,7 +855,7 @@ static void process_arrangeable(const ArrangePolygon &arrpoly,
     item.binId(arrpoly.bed_idx);
     item.priority(arrpoly.priority);
     item.itemId(arrpoly.itemid);
-    item.extrude_id = arrpoly.extrude_ids.front();
+    item.extrude_ids = arrpoly.extrude_ids;
     item.height = arrpoly.height;
     item.name = arrpoly.name;
     //BBS: add virtual object logic