diff --git a/datastore/sql/sqliteds.nim b/datastore/sql/sqliteds.nim
index 0f763d1..6d916d5 100644
--- a/datastore/sql/sqliteds.nim
+++ b/datastore/sql/sqliteds.nim
@@ -15,7 +15,7 @@ export backend, sqlitedsdb
 push: {.upraises: [].}
 
 type
-  SQLiteBackend*[K, V] = object
+  SQLiteBackend*[K: DbKey, V: DbVal] = object
     db: SQLiteDsDb[K, V]
 
 proc path*[K,V](self: SQLiteBackend[K,V]): string =
diff --git a/datastore/sql/sqlitedsdb.nim b/datastore/sql/sqlitedsdb.nim
index 95a1550..a8d4f41 100644
--- a/datastore/sql/sqlitedsdb.nim
+++ b/datastore/sql/sqlitedsdb.nim
@@ -26,7 +26,7 @@ type
   EndStmt* = NoParamsStmt
   RollbackStmt* = NoParamsStmt
 
-  SQLiteDsDb*[K,V] = object
+  SQLiteDsDb*[K: DbKey, V: DbVal] = object
     readOnly*: bool
     dbPath*: DataBuffer
     containsStmt*: ContainsStmt[K]