diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index e9cdb620e0..4aa45a60ed 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -6308,8 +6308,13 @@ LayerResult GCode::process_layer(
                                 all_label_ids.insert(inst.label_object_id);
                         break;
                     }
-            std::vector<size_t> filament_instances_id(all_label_ids.begin(), all_label_ids.end());
-            m_filament_instances_code = _encode_label_ids_to_base64(filament_instances_id);
+            // Orca: A scheduled extruder may have no object instances on this layer.
+            // Clear any pending mask so it cannot be emitted for the wrong toolchange.
+            m_filament_instances_code.clear();
+            if (!all_label_ids.empty()) {
+                std::vector<size_t> filament_instances_id(all_label_ids.begin(), all_label_ids.end());
+                m_filament_instances_code = _encode_label_ids_to_base64(filament_instances_id);
+            }
         }
 
         // The inline _extrude hook may already have taken the snapshot mid-extrusion on a