diff --git a/src/admesh/stl.h b/src/admesh/stl.h
index ac51ae1b68..2244aff2f2 100644
--- a/src/admesh/stl.h
+++ b/src/admesh/stl.h
@@ -165,6 +165,7 @@ struct indexed_triangle_set
     std::vector<stl_vertex>       				vertices;
 
     bool empty() const { return indices.empty() || vertices.empty(); }
+    bool operator==(const indexed_triangle_set& other) const { return this->indices == other.indices && this->vertices == other.vertices; }
 };
 
 extern bool stl_open(stl_file *stl, const char *file);
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 7d710849fc..ba56acaea4 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -3567,9 +3567,14 @@ bool Plater::priv::replace_volume_with_stl(int object_idx, int volume_idx, const
         new_volume->convert_from_imperial_units();
     else if (old_volume->source.is_converted_from_meters)
         new_volume->convert_from_meters();
-    new_volume->supported_facets.assign(old_volume->supported_facets);
-    new_volume->seam_facets.assign(old_volume->seam_facets);
-    new_volume->mmu_segmentation_facets.assign(old_volume->mmu_segmentation_facets);
+
+    if (old_volume->mesh().its == new_volume->mesh().its) {
+        // This function is called both from reload_from_disk and replace_with_stl.
+        // We need to make sure that the painted data point to existing triangles.
+        new_volume->supported_facets.assign(old_volume->supported_facets);
+        new_volume->seam_facets.assign(old_volume->seam_facets);
+        new_volume->mmu_segmentation_facets.assign(old_volume->mmu_segmentation_facets);
+    }
     std::swap(old_model_object->volumes[volume_idx], old_model_object->volumes.back());
     old_model_object->delete_volume(old_model_object->volumes.size() - 1);
     if (!sinking)