diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index a5e3cd23f..5230b066b 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -25,14 +25,20 @@ const static bool g_wipe_into_objects = false;
 
 
 // Shortest hamilton path problem
-static std::vector<unsigned int> solve_extruder_order(const std::vector<std::vector<float>>& wipe_volumes, std::vector<unsigned int> all_extruders, unsigned int start_extruder_id) 
+static std::vector<unsigned int> solve_extruder_order(const std::vector<std::vector<float>>& wipe_volumes, std::vector<unsigned int> all_extruders, std::optional<unsigned int> start_extruder_id) 
 {
-    auto start_iter = std::find(all_extruders.begin(), all_extruders.end(), start_extruder_id);
     bool add_start_extruder_flag = false;
-    if (start_iter == all_extruders.end())
-        all_extruders.insert(all_extruders.begin(), start_extruder_id), add_start_extruder_flag = true;
-    else
-        std::swap(*all_extruders.begin(), *start_iter);
+
+    if (start_extruder_id) {
+        auto start_iter = std::find(all_extruders.begin(), all_extruders.end(), start_extruder_id);
+        if (start_iter == all_extruders.end())
+            all_extruders.insert(all_extruders.begin(), *start_extruder_id), add_start_extruder_flag = true;
+        else
+            std::swap(*all_extruders.begin(), *start_iter);
+    }
+    else {
+        *start_extruder_id = all_extruders.front();
+    }
 
     unsigned int iterations = (1 << all_extruders.size());
     unsigned int final_state = iterations - 1;
@@ -84,7 +90,7 @@ static std::vector<unsigned int> solve_extruder_order(const std::vector<std::vec
     return path;
 }
 
-std::vector<unsigned int> get_extruders_order(const std::vector<std::vector<float>> &wipe_volumes, std::vector<unsigned int> all_extruders, unsigned int start_extruder_id)
+std::vector<unsigned int> get_extruders_order(const std::vector<std::vector<float>> &wipe_volumes, std::vector<unsigned int> all_extruders, std::optional<unsigned int>start_extruder_id)
 {
 #define USE_DP_OPTIMIZE
 #ifdef USE_DP_OPTIMIZE
@@ -823,10 +829,11 @@ void ToolOrdering::reorder_extruders_for_minimum_flush_volume()
     for (unsigned int i = 0; i < number_of_extruders; ++i)
         wipe_volumes.push_back(std::vector<float>(flush_matrix.begin() + i * number_of_extruders, flush_matrix.begin() + (i + 1) * number_of_extruders));
 
-    auto extruders_to_hash_key = [](const std::vector<unsigned int>& extruders, unsigned int initial_extruder_id)->uint32_t {
+    auto extruders_to_hash_key = [](const std::vector<unsigned int>& extruders, std::optional<unsigned int>initial_extruder_id)->uint32_t {
         uint32_t hash_key = 0;
         // high 16 bit define initial extruder ,low 16 bit define extruder set
-        hash_key |= (1 << (16 + initial_extruder_id));
+        if (initial_extruder_id)
+            hash_key |= (1 << (16 + *initial_extruder_id));
         for (auto item : extruders)
             hash_key |= (1 << item);
         return hash_key;
@@ -853,7 +860,7 @@ void ToolOrdering::reorder_extruders_for_minimum_flush_volume()
         return false;
     };
 
-    unsigned int current_extruder_id = -1;
+    std::optional<unsigned int>current_extruder_id;
     for (int i = 0; i < m_layer_tools.size(); ++i) {
         LayerTools& lt = m_layer_tools[i];
         if (lt.extruders.empty())
diff --git a/src/slic3r/Utils/FontUtils.cpp b/src/slic3r/Utils/FontUtils.cpp
index e7bc0c0e7..733038c2c 100644
--- a/src/slic3r/Utils/FontUtils.cpp
+++ b/src/slic3r/Utils/FontUtils.cpp
@@ -83,7 +83,7 @@ fontinfo_opt load_font_info(const unsigned char *data, unsigned int index)
     stbtt_fontinfo font_info;
     if (stbtt_InitFont(&font_info, data, font_offset) == 0) {
         // Can't initialize font.
-        assert(false);
+        //assert(false);
         return {};
     }
     return font_info;