diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 4b140c5b0..f748283a5 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -3127,12 +3127,12 @@ void Sidebar::sync_ams_list(bool is_from_big_sync_btn)
 
         for (size_t i = 0; i < merge_info.merges.size(); i++) {
             auto& cur = merge_info.merges[i];
-            for (size_t j = cur.size() -1; j >= 1 ; j--) {
+            for (int j = cur.size() -1; j >= 1 ; j--) {
                 auto last_index = cur[j];
                 change_filament(last_index, cur[0]);
                 cur.erase(cur.begin() + j);
                 sync_ams_badges.erase(sync_ams_badges.begin() + last_index);
-                reduce_index(merge_info, cur[j]);
+                reduce_index(merge_info, last_index);
             }
         }
         for (size_t i = 0; i < sync_ams_badges.size(); i++) {
diff --git a/src/slic3r/GUI/SyncAmsInfoDialog.cpp b/src/slic3r/GUI/SyncAmsInfoDialog.cpp
index e885aacc1..862a147f4 100644
--- a/src/slic3r/GUI/SyncAmsInfoDialog.cpp
+++ b/src/slic3r/GUI/SyncAmsInfoDialog.cpp
@@ -291,8 +291,8 @@ void SyncAmsInfoDialog::deal_ok()
         m_result.sync_maps.clear();
         for (size_t i = 0; i < m_ams_mapping_result.size(); i++) {
             auto temp_idx = m_ams_mapping_result[i].id;
-            if (temp_idx >= 0 && temp_idx < m_result.sync_maps.size()) {
-                auto &temp   = m_result.sync_maps[m_ams_mapping_result[i].id];
+            if (temp_idx >= 0) {
+                auto &temp   = m_result.sync_maps[temp_idx];
                 temp.ams_id  = m_ams_mapping_result[i].ams_id;
                 temp.slot_id = m_ams_mapping_result[i].slot_id;
             }