diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h
index a4c4bca..11b46bf 100644
--- a/libraries/liblmdb/lmdb.h
+++ b/libraries/liblmdb/lmdb.h
@@ -1410,7 +1410,10 @@ int mdb_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
*
* - #MDB_CURRENT - replace the item at the current cursor position.
* The \b key parameter must still be provided, and must match it.
- * So must \b data if using sorted duplicates (#MDB_DUPSORT).
+ * If using sorted duplicates (#MDB_DUPSORT) the data item must still
+ * sort into the same place. This is intended to be used when the
+ * new data is the same size as the old. Otherwise it will simply
+ * perform a delete of the old record followed by an insert.
*
- #MDB_NODUPDATA - enter the new key/data pair only if it does not
* already appear in the database. This flag may only be specified
* if the database was opened with #MDB_DUPSORT. The function will