diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index bf1d24e8a..8e48a56d6 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -201,12 +201,13 @@ std::string WipeTowerIntegration::append_tcr(GCode &gcodegen, const WipeTower::T
     // Let the m_writer know the current extruder_id, but ignore the generated G-code.
 	if (new_extruder_id >= 0 && gcodegen.writer().need_toolchange(new_extruder_id))
         gcodegen.writer().toolchange(new_extruder_id);
+    gcodegen.placeholder_parser().set("current_extruder", new_extruder_id);
+
     // Always append the filament start G-code even if the extruder did not switch,
     // because the wipe tower resets the linear advance and we want it to be re-enabled.
     const std::string &start_filament_gcode = gcodegen.config().start_filament_gcode.get_at(new_extruder_id);
     if (! start_filament_gcode.empty()) {
         // Process the start_filament_gcode for the active filament only.
-        gcodegen.placeholder_parser().set("current_extruder", new_extruder_id);
         DynamicConfig config;
         config.set_key_value("filament_extruder_id", new ConfigOptionInt(new_extruder_id));
         gcode += gcodegen.placeholder_parser_process("start_filament_gcode", start_filament_gcode, new_extruder_id, &config);
diff --git a/src/libslic3r/SLAPrint.hpp b/src/libslic3r/SLAPrint.hpp
index f43c3bf7a..64b2160b0 100644
--- a/src/libslic3r/SLAPrint.hpp
+++ b/src/libslic3r/SLAPrint.hpp
@@ -176,6 +176,8 @@ private:
         {
             return level<T>(r1) < level<T>(r2);
         });
+        
+        if(it == cont.end()) return it;
 
         T diff = std::abs(level<T>(*it) - lvl);
 
diff --git a/src/slic3r/GUI/GUI_App.cpp b/src/slic3r/GUI/GUI_App.cpp
index 4eb6c5aa8..c8e411ee4 100644
--- a/src/slic3r/GUI/GUI_App.cpp
+++ b/src/slic3r/GUI/GUI_App.cpp
@@ -44,6 +44,10 @@
 #include "SysInfoDialog.hpp"
 #include "KBShortcutsDialog.hpp"
 
+#ifdef __WXMSW__
+#include <Shlobj.h>
+#endif // __WXMSW__
+
 namespace Slic3r {
 namespace GUI {
 
@@ -182,6 +186,10 @@ bool GUI_App::on_init_inner()
     app_config->set("version", SLIC3R_VERSION);
     app_config->save();
 
+#ifdef __WXMSW__
+    associate_3mf_files();
+#endif // __WXMSW__
+
     preset_updater = new PresetUpdater();
     Bind(EVT_SLIC3R_VERSION_ONLINE, [this](const wxCommandEvent &evt) {
         app_config->set("version_online", into_u8(evt.GetString()));
@@ -951,5 +959,64 @@ void GUI_App::window_pos_sanitize(wxTopLevelWindow* window)
 // }
 
 
+#ifdef __WXMSW__
+void GUI_App::associate_3mf_files()
+{
+    // see as reference: https://stackoverflow.com/questions/20245262/c-program-needs-an-file-association
+
+    auto reg_set = [](HKEY hkeyHive, const wchar_t* pszVar, const wchar_t* pszValue)
+    {
+        wchar_t szValueCurrent[1000];
+        DWORD dwType;
+        DWORD dwSize = sizeof(szValueCurrent);
+
+        int iRC = ::RegGetValueW(hkeyHive, pszVar, nullptr, RRF_RT_ANY, &dwType, szValueCurrent, &dwSize);
+
+        bool bDidntExist = iRC == ERROR_FILE_NOT_FOUND;
+
+        if ((iRC != ERROR_SUCCESS) && !bDidntExist)
+            // an error occurred
+            return;
+
+        if (!bDidntExist)
+        {
+            if (dwType != REG_SZ)
+                // invalid type
+                return;
+
+            if (::wcscmp(szValueCurrent, pszValue) == 0)
+                // value already set
+                return;
+        }
+
+        DWORD dwDisposition;
+        HKEY hkey;
+        iRC = ::RegCreateKeyExW(hkeyHive, pszVar, 0, 0, 0, KEY_ALL_ACCESS, nullptr, &hkey, &dwDisposition);
+        if (iRC == ERROR_SUCCESS)
+            iRC = ::RegSetValueExW(hkey, L"", 0, REG_SZ, (BYTE*)pszValue, (::wcslen(pszValue) + 1) * sizeof(wchar_t));
+
+        RegCloseKey(hkey);
+    };
+
+    wchar_t app_path[MAX_PATH];
+    ::GetModuleFileNameW(nullptr, app_path, sizeof(app_path));
+
+    std::wstring prog_path = L"\"" + std::wstring(app_path) + L"\"";
+    std::wstring prog_id = L"Prusa.Slicer.1";
+    std::wstring prog_desc = L"PrusaSlicer";
+    std::wstring prog_command = prog_path + L" \"%1\"";
+    std::wstring reg_base = L"Software\\Classes";
+    std::wstring reg_extension = reg_base + L"\\.3mf";
+    std::wstring reg_prog_id = reg_base + L"\\" + prog_id;
+    std::wstring reg_prog_id_command = reg_prog_id + L"\\Shell\\Open\\Command";
+
+    reg_set(HKEY_CURRENT_USER, reg_extension.c_str(), prog_id.c_str());
+    reg_set(HKEY_CURRENT_USER, reg_prog_id.c_str(), prog_desc.c_str());
+    reg_set(HKEY_CURRENT_USER, reg_prog_id_command.c_str(), prog_command.c_str());
+
+    ::SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, nullptr, nullptr);
+}
+#endif // __WXMSW__
+
 } // GUI
 } //Slic3r
diff --git a/src/slic3r/GUI/GUI_App.hpp b/src/slic3r/GUI/GUI_App.hpp
index 5c2ead49c..716bb8fd0 100644
--- a/src/slic3r/GUI/GUI_App.hpp
+++ b/src/slic3r/GUI/GUI_App.hpp
@@ -178,6 +178,9 @@ private:
     void            window_pos_save(wxTopLevelWindow* window, const std::string &name);
     void            window_pos_restore(wxTopLevelWindow* window, const std::string &name, bool default_maximized = false);
     void            window_pos_sanitize(wxTopLevelWindow* window);
+#ifdef __WXMSW__
+    void associate_3mf_files();
+#endif // __WXMSW__
 };
 DECLARE_APP(GUI_App)