From ee6613a4b8b0720723518c823ef815c4be9d64d4 Mon Sep 17 00:00:00 2001
From: Kiss Lorand <50251547+kisslorand@users.noreply.github.com>
Date: Wed, 12 Aug 2026 21:18:00 +0300
Subject: [PATCH] Fix stale flush matrix after enabling SEMM (#15223)

---
 src/libslic3r/PresetBundle.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libslic3r/PresetBundle.cpp b/src/libslic3r/PresetBundle.cpp
index 01cbc43bc2..5557d36891 100644
--- a/src/libslic3r/PresetBundle.cpp
+++ b/src/libslic3r/PresetBundle.cpp
@@ -5378,7 +5378,7 @@ void PresetBundle::update_multi_material_filament_presets(size_t to_delete_filam
         f_multiplier.resize(nozzle_nums, 1.f);
     }
 
-    if ( (num_filaments * num_filaments) != size_t(old_matrix.size() / old_nozzle_nums) ) {
+    if (old_matrix.size() != num_filaments * num_filaments * nozzle_nums) {
         // First verify if purging volumes presets for each extruder matches number of extruders
         std::vector<double>& filaments = this->project_config.option<ConfigOptionFloats>("flush_volumes_vector")->values;
         while (filaments.size() < 2* num_filaments) {