diff --git a/ledis/t_set.go b/ledis/t_set.go
index 51458bb0..ae58e3a2 100644
--- a/ledis/t_set.go
+++ b/ledis/t_set.go
@@ -490,7 +490,6 @@ func (db *DB) sStoreGeneric(dstKey []byte, optType byte, keys ...[]byte) (int64,
 
 	var err error
 	var ek []byte
-	var num int64 = 0
 	var v [][]byte
 
 	switch optType {
@@ -513,22 +512,21 @@ func (db *DB) sStoreGeneric(dstKey []byte, optType byte, keys ...[]byte) (int64,
 
 		ek = db.sEncodeSetKey(dstKey, m)
 
-		if v, err := db.db.Get(ek); err != nil {
+		if _, err := db.db.Get(ek); err != nil {
 			return 0, err
-		} else if v == nil {
-			num++
 		}
 
 		t.Put(ek, nil)
-
 	}
 
-	if _, err = db.sIncrSize(dstKey, num); err != nil {
+	var num = int64(len(v))
+	sk := db.sEncodeSizeKey(dstKey)
+	t.Put(sk, PutInt64(num))
+
+	if err = t.Commit(); err != nil {
 		return 0, err
 	}
-
-	err = t.Commit()
-	return num, err
+	return num, nil
 }
 
 func (db *DB) SClear(key []byte) (int64, error) {
diff --git a/ledis/t_set_test.go b/ledis/t_set_test.go
index c5f65238..110a9829 100644
--- a/ledis/t_set_test.go
+++ b/ledis/t_set_test.go
@@ -147,7 +147,7 @@ func testUnion(db *DB, t *testing.T) {
 	m2 := []byte("m2")
 	m3 := []byte("m3")
 	db.SAdd(key, m1, m2)
-	db.SAdd(key1, m1, m3)
+	db.SAdd(key1, m1, m2, m3)
 	db.SAdd(key2, m2, m3)
 	if _, err := db.sUnionGeneric(key, key2); err != nil {
 		t.Fatal(err)
@@ -158,11 +158,13 @@ func testUnion(db *DB, t *testing.T) {
 	}
 
 	dstkey := []byte("union_dsk")
+	db.SAdd(dstkey, []byte("x"))
 	if num, err := db.SUnionStore(dstkey, key1, key2); err != nil {
 		t.Fatal(err)
 	} else if num != 3 {
 		t.Fatal(num)
 	}
+
 	if _, err := db.SMembers(dstkey); err != nil {
 		t.Fatal(err)
 	}