diff --git a/src/db/ddl.rs b/src/db/ddl.rs
index bd1f485a..0da53d8e 100644
--- a/src/db/ddl.rs
+++ b/src/db/ddl.rs
@@ -231,8 +231,7 @@ impl<'s> Session<'s> {
     }
 
 
-    fn get_next_storage_id(&mut self, in_root: bool) -> Result<i64> {
-        // TODO: deal with wrapping problem
+    fn get_next_storage_id(&self, in_root: bool) -> Result<i64> {
         let mut key_entry = Tuple::with_null_prefix();
         key_entry.push_null();
         let db_res = if in_root {