diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 902786bf7d..12a3a73e7c 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -9474,12 +9474,14 @@ std::string GCode::set_extruder(unsigned int new_filament_id, double print_z, bo
             if (old_filament_id_in_new_extruder == -1)
                 wipe_volume = 0;
             else {
-                wipe_volume = flush_matrix[old_filament_id_in_new_extruder * number_of_extruders + new_filament_id];
+                size_t flush_idx = size_t(old_filament_id_in_new_extruder) * number_of_extruders + new_filament_id;
+                wipe_volume = flush_idx < flush_matrix.size() ? flush_matrix[flush_idx] : 0.f;
                 wipe_volume *= m_config.flush_multiplier.get_at(new_extruder_id);
             }
         }
         else {
-            wipe_volume = flush_matrix[old_filament_id * number_of_extruders + new_filament_id];
+            size_t flush_idx = size_t(old_filament_id) * number_of_extruders + new_filament_id;
+            wipe_volume = flush_idx < flush_matrix.size() ? flush_matrix[flush_idx] : 0.f;
             wipe_volume *= m_config.flush_multiplier.get_at(new_extruder_id);  // if is multi_extruder only use the fist extruder matrix
         }
         wipe_volume = std::max(0.f, wipe_volume-grab_purge_volume);
diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index e4da19cd73..6fc7717386 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -7596,8 +7596,8 @@ void GCodeProcessor::update_slice_warnings()
         if (used_filaments[idx] < m_result.required_nozzle_HRC.size())
             filament_hrc = m_result.required_nozzle_HRC[used_filaments[idx]];
 
-        int filament_extruder_id = m_filament_maps[used_filaments[idx]];
-        int extruder_hrc = nozzle_hrc_lists[filament_extruder_id];
+        int filament_extruder_id = used_filaments[idx] < m_filament_maps.size() ? m_filament_maps[used_filaments[idx]] : -1;
+        int extruder_hrc = (filament_extruder_id >= 0 && (size_t) filament_extruder_id < nozzle_hrc_lists.size()) ? nozzle_hrc_lists[filament_extruder_id] : 0;
 
         BOOST_LOG_TRIVIAL(debug) << __FUNCTION__ << boost::format(": Check HRC: filament:%1%, hrc=%2%, extruder:%3%, hrc:%4%") % used_filaments[idx] % filament_hrc % filament_extruder_id % extruder_hrc;