Why django test --keep-db works with postgres database but not with default sqlite3

I'm testing Django (v1.11.4) application in two setups of database: 1) postgres database running in docker container or 2) sqlite3 as (defaulut database)

When running tests with --keep-db option I observe different behavior for these two setups: for postgres --keep-db works as expected (there is no database creation and running test is fast) but for sqlite3 database --keep-db seems not working (for each run of the test there is creation of database). Is it possible to have --keep-db working with sqlite3? If so any idea what settings might affect behavior described as above?