diff --git a/src/libslic3r/CustomGCode.hpp b/src/libslic3r/CustomGCode.hpp
index 334b40431..c4a47b9a3 100644
--- a/src/libslic3r/CustomGCode.hpp
+++ b/src/libslic3r/CustomGCode.hpp
@@ -66,6 +66,8 @@ struct Info
 
     bool operator==(const Info& rhs) const
     {
+        if (rhs.gcodes.empty() && this->gcodes.empty())
+            return true; // don't respect to the comparison of the mode, when g_codes are empty
         return  (rhs.mode   == this->mode   ) &&
                 (rhs.gcodes == this->gcodes );
     }
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 36f2f3861..14562a20d 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -3317,6 +3317,7 @@ unsigned int Plater::priv::update_background_process(bool force_validation, bool
 
         sidebar->set_btn_label(ActionButtonType::abExport, _(label_btn_export));
         sidebar->set_btn_label(ActionButtonType::abSendGCode, _(label_btn_send));
+        dirty_state.update_from_preview();
 
         const wxString slice_string = background_process.running() && wxGetApp().get_mode() == comSimple ?
                                       _L("Slicing") + dots : _L("Slice now");
diff --git a/src/slic3r/GUI/ProjectDirtyStateManager.cpp b/src/slic3r/GUI/ProjectDirtyStateManager.cpp
index 89c13b640..d30e5d510 100644
--- a/src/slic3r/GUI/ProjectDirtyStateManager.cpp
+++ b/src/slic3r/GUI/ProjectDirtyStateManager.cpp
@@ -7,6 +7,8 @@
 #include "I18N.hpp"
 #include "Plater.hpp"
 
+#include "libslic3r/Model.hpp"
+
 #include <boost/algorithm/string/predicate.hpp>
 
 #include <algorithm>
@@ -38,12 +40,18 @@ void ProjectDirtyStateManager::update_from_presets()
     app.mainframe->update_title();
 }
 
+void ProjectDirtyStateManager::update_from_preview()
+{
+    m_custom_gcode_per_print_z_dirty = m_initial_custom_gcode_per_print_z != wxGetApp().model().custom_gcode_per_print_z;
+}
+
 void ProjectDirtyStateManager::reset_after_save()
 {
     this->reset_initial_presets();
     m_plater_dirty  = false;
     m_presets_dirty = false;
     m_project_config_dirty = false;
+    m_custom_gcode_per_print_z_dirty = false;
     wxGetApp().mainframe->update_title();
 }
 
@@ -54,6 +62,7 @@ void ProjectDirtyStateManager::reset_initial_presets()
     for (const PresetCollection *preset_collection : app.get_active_preset_collections())
         m_initial_presets[preset_collection->type()] = preset_collection->get_selected_preset_name();
     m_initial_project_config = app.preset_bundle->project_config;
+    m_initial_custom_gcode_per_print_z = app.model().custom_gcode_per_print_z;
 }
 
 #if ENABLE_PROJECT_DIRTY_STATE_DEBUG_WINDOW
diff --git a/src/slic3r/GUI/ProjectDirtyStateManager.hpp b/src/slic3r/GUI/ProjectDirtyStateManager.hpp
index 6841c89c6..e4e2668fd 100644
--- a/src/slic3r/GUI/ProjectDirtyStateManager.hpp
+++ b/src/slic3r/GUI/ProjectDirtyStateManager.hpp
@@ -2,6 +2,7 @@
 #define slic3r_ProjectDirtyStateManager_hpp_
 
 #include "libslic3r/Preset.hpp"
+#include "libslic3r/CustomGCode.hpp"
 
 namespace Slic3r {
 namespace GUI {
@@ -11,10 +12,11 @@ class ProjectDirtyStateManager
 public:    
     void update_from_undo_redo_stack(bool dirty);
     void update_from_presets();
+    void update_from_preview();
     void reset_after_save();
     void reset_initial_presets();
 
-    bool is_dirty() const { return m_plater_dirty || m_project_config_dirty || m_presets_dirty; }
+    bool is_dirty() const { return m_plater_dirty || m_project_config_dirty || m_presets_dirty || m_custom_gcode_per_print_z_dirty; }
     bool is_presets_dirty() const { return m_presets_dirty; }
 
 #if ENABLE_PROJECT_DIRTY_STATE_DEBUG_WINDOW
@@ -28,9 +30,12 @@ private:
     bool                                        m_presets_dirty { false };
     // Is the project config dirty?
     bool                                        m_project_config_dirty { false };
+    // Is the custom_gcode_per_print_z dirty?
+    bool                                        m_custom_gcode_per_print_z_dirty { false };
     // Keeps track of preset names selected at the time of last project save.
     std::array<std::string, Preset::TYPE_COUNT> m_initial_presets;
     DynamicPrintConfig                          m_initial_project_config;
+    CustomGCode::Info                           m_initial_custom_gcode_per_print_z;
 };
 
 } // namespace GUI