diff --git a/src/SCAN/Scan_Thread_Data.cc b/src/SCAN/Scan_Thread_Data.cc
index f75fbcb..e2da0d1 100644
--- a/src/SCAN/Scan_Thread_Data.cc
+++ b/src/SCAN/Scan_Thread_Data.cc
@@ -29,6 +29,7 @@ namespace ABACUS {
   {
     label = RefThread.label;
     type = RefThread.type;
+    return *this;
   }
 
 
@@ -150,7 +151,7 @@ namespace ABACUS {
 
     int il_used = lowest_il_with_nthreads_neq_0;
     Vect<Scan_Thread> next_in_line(nthreads_total[il_used]);
-
+    
     // Copy the in-memory threads
     for (int it = 0; it < nthreads_in_memory[il_used]; ++it) {
       next_in_line[it] = Scan_Thread(label[il_used][it], type[il_used][it]);