diff --git a/src/Development/IDE/State/Service.hs b/src/Development/IDE/State/Service.hs
index ff0e173a..6d83cd8b 100644
--- a/src/Development/IDE/State/Service.hs
+++ b/src/Development/IDE/State/Service.hs
@@ -13,7 +13,7 @@ module Development.IDE.State.Service(
     getServiceEnv,
     IdeState, initialise, shutdown,
     runAction, runActions,
-    setFilesOfInterest,
+    setFilesOfInterest, modifyFilesOfInterest,
     writeProfile,
     getDiagnostics, unsafeClearDiagnostics,
     logDebug, logSeriousError
@@ -26,6 +26,8 @@ import           Development.IDE.State.FileStore
 import qualified Development.IDE.Logger as Logger
 import           Data.Set                                 (Set)
 import qualified Data.Set                                 as Set
+import qualified Data.Text as T
+import Data.Tuple.Extra
 import           Development.IDE.Functions.GHCError
 import Development.IDE.Types.Diagnostics (NormalizedFilePath)
 import           Development.Shake                        hiding (Diagnostic, Env, newCache)
@@ -109,12 +111,13 @@ runActions x = join . shakeRun x
 
 -- | Set the files-of-interest which will be built and kept-up-to-date.
 setFilesOfInterest :: IdeState -> Set NormalizedFilePath -> IO ()
-setFilesOfInterest state files = do
-    Env{..} <- getIdeGlobalState state
-    -- update vars synchronously
-    modifyVar_ envOfInterestVar $ const $ return files
+setFilesOfInterest state files = modifyFilesOfInterest state (const files)
 
-    -- run shake to update results regarding the files of interest
+modifyFilesOfInterest :: IdeState -> (Set NormalizedFilePath -> Set NormalizedFilePath) -> IO ()
+modifyFilesOfInterest state f = do
+    Env{..} <- getIdeGlobalState state
+    files <- modifyVar envOfInterestVar $ pure . dupe . f
+    logDebug state $ "Set files of interest to: " <> T.pack (show $ Set.toList files)
     void $ shakeRun state []
 
 getServiceEnv :: Action Env