diff --git a/orm/db.go b/orm/db.go
index e488a5ab..8e7e93bb 100644
--- a/orm/db.go
+++ b/orm/db.go
@@ -631,10 +631,10 @@ func (d *dbBase) Update(q dbQuerier, mi *modelInfo, ind reflect.Value, tz *time.
 	}
 
 	if find {
-		newSetNames := make([]string, 0, 0)
+		newSetNames := make([]string, 0, len(setNames)-1)
 		newSetNames = append(setNames[0:index], setNames[index+1:]...)
 		setNames = newSetNames
-		newSetValues := make([]interface{}, 0, 0)
+		newSetValues := make([]interface{}, 0, len(setNames)-1)
 		newSetValues = append(setValues[0:index], setValues[index+1:]...)
 		setValues = newSetValues