diff --git a/dialect.go b/dialect.go
index a463aad..e641035 100644
--- a/dialect.go
+++ b/dialect.go
@@ -136,7 +136,7 @@ func (d PostgresDialect) ToSqlType(val reflect.Type, maxsize int, isAutoIncr boo
 		return "integer"
 	case reflect.Int64:
 		if isAutoIncr {
-			return "serial"
+			return "bigserial"
 		}
 		return "bigint"
 	case reflect.Float64, reflect.Float32: