diff --git a/spec/cached.cr b/spec/cached.cr
index 7a09cee..c9dd575 100644
--- a/spec/cached.cr
+++ b/spec/cached.cr
@@ -71,6 +71,7 @@ describe "DODB::DataBase::Cached" do
 			db2 = DODB::SpecDataBase.new remove_previous_data: false
 			db2 << Ship.mutsuki
 
+			# Only difference with DODB::DataBase: for now, concurrent DB cannot coexists.
 			db2.to_a.size.should eq(2)
 		end