diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index acc3bf2050..3d1298f3e3 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -169,6 +169,11 @@ ToolOrdering::ToolOrdering(const Print &print, unsigned int first_extruder, bool
     this->fill_wipe_tower_partitions(print.config(), object_bottom_z, max_layer_height);
 
     if (this->insert_wipe_tower_extruder()) {
+        // Now convert the 0-based list to 1-based again, because that is what reorder_extruder expects.
+        for (LayerTools& lt : m_layer_tools) {
+            for (auto& extruder : lt.extruders)
+                    ++extruder;
+        }
         this->reorder_extruders(first_extruder);
         this->fill_wipe_tower_partitions(print.config(), object_bottom_z, max_layer_height);
     }
@@ -470,16 +475,15 @@ void ToolOrdering::fill_wipe_tower_partitions(const PrintConfig &config, coordf_
 bool ToolOrdering::insert_wipe_tower_extruder()
 {
     // In case that wipe_tower_extruder is set to non-zero, we must make sure that the extruder will be in the list.
-    // The list is 1-based, as is the config value !
     bool changed = false;
     if (m_print_config_ptr->wipe_tower_extruder != 0) {
         for (LayerTools& lt : m_layer_tools) {
             if (lt.wipe_tower_partitions > 0) {
-                lt.extruders.emplace_back(m_print_config_ptr->wipe_tower_extruder);
+                lt.extruders.emplace_back(m_print_config_ptr->wipe_tower_extruder - 1);
                 sort_remove_duplicates(lt.extruders);
                 changed = true;
             }
-        }
+        }  
     }
     return changed;
 }