diff --git a/src/libslic3r/Arrange/Core/NFP/NFP.cpp b/src/libslic3r/Arrange/Core/NFP/NFP.cpp
index e96581b80d..99a25edfdb 100644
--- a/src/libslic3r/Arrange/Core/NFP/NFP.cpp
+++ b/src/libslic3r/Arrange/Core/NFP/NFP.cpp
@@ -279,11 +279,11 @@ void nfp_convex_convex(const Polygon &fixed, const Polygon &movable, Polygon &po
 
     // Output iterator adapter for std::merge
     struct OutItAdaptor {
-        using value_type = Line;
-        using difference_type = std::ptrdiff_t;
-        using pointer = Line*;
-        using reference = Line&;
-        using iterator_category = std::output_iterator_tag;
+        using value_type [[maybe_unused]] = Line;
+        using difference_type [[maybe_unused]] = std::ptrdiff_t;
+        using pointer [[maybe_unused]] = Line*;
+        using reference [[maybe_unused]] = Line& ;
+        using iterator_category [[maybe_unused]] = std::output_iterator_tag;
 
         Polygon *outpoly;
         OutItAdaptor(Polygon &out) : outpoly{&out} {}