diff --git a/Objects/setobject.c b/Objects/setobject.c
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -285,8 +285,6 @@
   found_null:
     entry->key = key;
     entry->hash = hash;
-    so->fill++;
-    so->used++;
 }
 
 /* ======== End logic for probing the hash table ========================== */
@@ -356,8 +354,8 @@
     /* Make the set empty, using the new table. */
     assert(newtable != oldtable);
     memset(newtable, 0, sizeof(setentry) * newsize);
-    so->fill = 0;
-    so->used = 0;
+    so->fill = oldused;
+    so->used = oldused;
     so->mask = newsize - 1;
     so->table = newtable;
 
@@ -676,6 +674,8 @@
 
     /* If our table is empty, we can use set_insert_clean() */
     if (so->fill == 0) {
+        so->fill = other->used;
+        so->used = other->used;
         for (i = 0; i <= other->mask; i++, other_entry++) {
             key = other_entry->key;
             if (key != NULL && key != dummy) {