diff --git a/src/libslic3r/PerimeterGenerator.cpp b/src/libslic3r/PerimeterGenerator.cpp
index 4fec834171..e99c458b2c 100644
--- a/src/libslic3r/PerimeterGenerator.cpp
+++ b/src/libslic3r/PerimeterGenerator.cpp
@@ -2916,10 +2916,11 @@ void PerimeterGenerator::process_arachne()
     });
     for (ArachneSurfaceResult &result : results) {
         if (result.has_loops)
-            this->loops->append(result.loops);
+            // Moved, not copied: append(const ExtrusionEntity &) clones the whole wall tree of the island.
+            this->loops->append(std::move(result.loops));
         this->fill_surfaces->append(result.infill, stInternal);
         apply_extra_perimeters(result.infill);
-        this->fill_no_overlap->insert(this->fill_no_overlap->end(), result.no_overlap.begin(), result.no_overlap.end());
+        append(*this->fill_no_overlap, std::move(result.no_overlap));
     }
 }