What is the cause of warning "WARNING in hptSomeThingsBelowUs, missing module ..." when invoking GHC API and how to get rid of it?

I was trying to use GHC API to load .hs files on the fly. I wrote two .hs files, test.hs and Module.hs, and put them into the /tmp folder. These two files are very simple. Module.hs defines a module called Module containing an Int value, and test.hs defines the module Test which imports Module and copies the Int value to itself. Their contents are shown below.


module Module (
) where

value_in_module = 1234 :: Int


module Test (
) where

import Module

value = value_in_module

Then in another file, I wrote the following code to invoke GHC API and load those two files.

import Control.Applicative
import DynFlags
import GHC
import GHC.Paths
import MonadUtils (liftIO)
import Unsafe.Coerce
import SimplCore (core2core)
main = defaultErrorHandler defaultFatalMessager defaultFlushOut $
    runGhc (Just libdir) $ do
        env <- getSession
        dflags <- getSessionDynFlags
        setSessionDynFlags $ dflags { hscTarget = HscInterpreted, ghcLink = LinkInMemory }

        setTargets =<< sequence [guessTarget "/tmp/Module.hs" Nothing, guessTarget "/tmp/test.hs" Nothing]
        load LoadAllTargets
        setContext [ IIModule $ mkModuleName "Test" ]

        -- The following six lines are just for reproducing the warning.
        modSum <- getModSummary $ mkModuleName "Test"
        pmod <- parseModule modSum
        tmod <- typecheckModule pmod
        dmod <- desugarModule tmod
        let core = coreModule dmod
        core' <- liftIO $ core2core env core -- Warning happens here.
        -- end
        act <- unsafeCoerce <$> compileExpr "print value"           
        liftIO act

The program runs, but with the following output.

WARNING in hptSomeThingsBelowUs
  missing module Module
  Probable cause: out-of-date interface files

We can notice that the program successfully evaluates the expression print value, and outputs 1234, but the function core2core emits the warning message above. The six lines between a pair of comments seem to have nothing to do with the rest of the program, because this is just a minimal reproducible example I extracted from another much larger project. Also the warning message does not hurt here, but it causes much more serious problems in that project. The GHC API seems not well documented, so I could not solve the problem after doing a lot of search. Could anyone explain the cause of the warning message, and help me deal with multiple files using GHC APIs? Thanks in advance.