diff --git a/src/Weeder.hs b/src/Weeder.hs
index 327b8a4..700a620 100644
--- a/src/Weeder.hs
+++ b/src/Weeder.hs
@@ -48,6 +48,7 @@ import qualified Data.Set as Set
 import Data.Generics.Labels ()
 
 -- ghc
+import GHC.Data.FastString ( unpackFS )
 import GHC.Types.Avail
   ( AvailInfo( Avail, AvailTC )
   , GreName( NormalGreName, FieldGreName )
@@ -61,7 +62,7 @@ import GHC.Iface.Ext.Types
   , HieASTs( HieASTs )
   , HieFile( HieFile, hie_asts, hie_exports, hie_module, hie_hs_file )
   , IdentifierDetails( IdentifierDetails, identInfo )
-  , NodeAnnotation( NodeAnnotation, nodeAnnotConstr, nodeAnnotType )
+  , NodeAnnotation( NodeAnnotation, nodeAnnotType )
   , NodeInfo( nodeIdentifiers, nodeAnnotations )
   , Scope( ModuleScope )
   , getSourcedNodeInfo
@@ -276,8 +277,8 @@ topLevelAnalysis n@Node{ nodeChildren } = do
 
 analyseBinding :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analyseBinding n@Node{ nodeSpan, sourcedNodeInfo } = do
-  let bindAnns = Set.fromList [(NodeAnnotation "FunBind" "HsBindLR"), (NodeAnnotation "PatBind" "HsBindLR")]
-  guard $ any (not . Set.disjoint bindAnns . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  let bindAnns = Set.fromList [("FunBind", "HsBindLR"), ("PatBind", "HsBindLR")]
+  guard $ any (not . Set.disjoint bindAnns . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   for_ ( findDeclarations n ) \d -> do
     define d nodeSpan
@@ -287,21 +288,21 @@ analyseBinding n@Node{ nodeSpan, sourcedNodeInfo } = do
 
 analyseRewriteRule :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analyseRewriteRule n@Node{ sourcedNodeInfo } = do
-  guard $ any (Set.member (NodeAnnotation "HsRule" "RuleDecl") . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  guard $ any (Set.member ("HsRule", "RuleDecl") . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   for_ ( uses n ) addImplicitRoot
 
 
 analyseInstanceDeclaration :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analyseInstanceDeclaration n@Node{ sourcedNodeInfo } = do
-  guard $ any (Set.member (NodeAnnotation "ClsInstD" "InstDecl") . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  guard $ any (Set.member ("ClsInstD", "InstDecl") . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   traverse_ addImplicitRoot ( uses n )
 
 
 analyseClassDeclaration :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analyseClassDeclaration n@Node{ sourcedNodeInfo } = do
-  guard $ any (Set.member (NodeAnnotation "ClassDecl" "TyClDecl") . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  guard $ any (Set.member ("ClassDecl", "TyClDecl") . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   for_ ( findIdentifiers isClassDeclaration n ) $
     for_ ( findIdentifiers ( const True ) n ) . addDependency
@@ -319,7 +320,7 @@ analyseClassDeclaration n@Node{ sourcedNodeInfo } = do
 
 analyseDataDeclaration :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analyseDataDeclaration n@Node{ sourcedNodeInfo } = do
-  guard $ any (Set.member (NodeAnnotation "DataDecl" "TyClDecl") . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  guard $ any (Set.member ("DataDecl", "TyClDecl") . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   for_
     ( foldMap
@@ -346,7 +347,7 @@ analyseDataDeclaration n@Node{ sourcedNodeInfo } = do
 
 constructors :: HieAST a -> Seq ( HieAST a )
 constructors n@Node{ nodeChildren, sourcedNodeInfo } =
-  if any (any ( ("ConDecl" ==) . nodeAnnotType ) . nodeAnnotations) (getSourcedNodeInfo sourcedNodeInfo) then
+  if any (any ( ("ConDecl" ==) . unpackFS . nodeAnnotType) . nodeAnnotations) (getSourcedNodeInfo sourcedNodeInfo) then
     pure n
 
   else
@@ -354,7 +355,7 @@ constructors n@Node{ nodeChildren, sourcedNodeInfo } =
 
 analysePatternSynonyms :: ( Alternative m, MonadState Analysis m ) => HieAST a -> m ()
 analysePatternSynonyms n@Node{ sourcedNodeInfo } = do
-  guard $ any (Set.member (NodeAnnotation "PatSynBind" "HsBindLR") . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
+  guard $ any (Set.member ("PatSynBind", "HsBindLR") . Set.map unNodeAnnotation . nodeAnnotations) $ getSourcedNodeInfo sourcedNodeInfo
 
   for_ ( findDeclarations n ) $ for_ ( uses n ) . addDependency
 
@@ -407,3 +408,7 @@ nameToDeclaration :: Name -> Maybe Declaration
 nameToDeclaration name = do
   m <- nameModule_maybe name
   return Declaration { declModule = m, declOccName = nameOccName name }
+
+
+unNodeAnnotation :: NodeAnnotation -> (String, String)
+unNodeAnnotation (NodeAnnotation x y) = (unpackFS x, unpackFS y)
diff --git a/src/Weeder/Main.hs b/src/Weeder/Main.hs
index 58291fe..be36273 100644
--- a/src/Weeder/Main.hs
+++ b/src/Weeder/Main.hs
@@ -9,11 +9,16 @@
 
 module Weeder.Main ( main, mainWithConfig ) where
 
+-- algebraic-graphs
+import Algebra.Graph.Export.Dot ( export, defaultStyleViaShow )
+
 -- base
+import Control.Exception ( evaluate )
 import Control.Monad ( guard, unless, when )
 import Control.Monad.IO.Class ( liftIO )
 import Data.Bool
 import Data.Foldable
+import Data.IORef ( atomicModifyIORef, newIORef, readIORef )
 import Data.List ( isSuffixOf )
 import Data.Version ( showVersion )
 import System.Exit ( exitFailure )
@@ -119,14 +124,13 @@ mainWithConfig hieExt hieDirectories requireHsFiles Config{ rootPatterns, typeCl
       then getFilesIn ".hs" "./."
       else pure []
 
-  nameCache <- do
-    uniqSupply <- mkSplitUniqSupply 'z'
-    return ( initNameCache uniqSupply [] )
+  nameCacheUpdater <-
+    mkNameCacheUpdater
 
   analysis <-
     flip execStateT emptyAnalysis do
       for_ hieFilePaths \hieFilePath -> do
-        hieFileResult <- liftIO ( readCompatibleHieFileOrExit nameCache hieFilePath )
+        hieFileResult <- liftIO ( readCompatibleHieFileOrExit nameCacheUpdater hieFilePath )
         let hsFileExists = any ( hie_hs_file hieFileResult `isSuffixOf` ) hsFilePaths
         when (requireHsFiles ==> hsFileExists) do
           analyseHieFile hieFileResult
@@ -216,9 +220,9 @@ getFilesIn ext path = do
 
 
 -- | Read a .hie file, exiting if it's an incompatible version.
-readCompatibleHieFileOrExit :: NameCache -> FilePath -> IO HieFile
-readCompatibleHieFileOrExit nameCache path = do
-  res <- readHieFileWithVersion (\(v, _) -> v == hieVersion) (NCU (\f -> return $ snd $ f nameCache)) path
+readCompatibleHieFileOrExit :: NameCacheUpdater -> FilePath -> IO HieFile
+readCompatibleHieFileOrExit nameCacheUpdater path = do
+  res <- readHieFileWithVersion (\(v, _) -> v == hieVersion) nameCacheUpdater path
   case res of
     Right HieFileResult{ hie_file_result } ->
       return hie_file_result
@@ -233,6 +237,19 @@ readCompatibleHieFileOrExit nameCache path = do
       exitFailure
 
 
+mkNameCacheUpdater :: IO NameCacheUpdater
+mkNameCacheUpdater = do
+  nameCache <- do
+    uniqSupply <- mkSplitUniqSupply 'z'
+    return ( initNameCache uniqSupply [] )
+
+  nameCacheRef <- newIORef nameCache
+
+  let update_nc f = do r <- atomicModifyIORef nameCacheRef f
+                       _ <- evaluate =<< readIORef nameCacheRef
+                       return r
+  return (NCU update_nc)
+
 
 infixr 5 ==>
 
diff --git a/weeder.cabal b/weeder.cabal
index cb729d4..d67b050 100644
--- a/weeder.cabal
+++ b/weeder.cabal
@@ -18,7 +18,7 @@ extra-doc-files:
 
 library
   build-depends:
-    , algebraic-graphs     ^>= 0.4 || ^>= 0.5
+    , algebraic-graphs     ^>= 0.4 || ^>= 0.5  || ^>= 0.6
     , base                 ^>= 4.16.0.0
     , bytestring           ^>= 0.10.9.0 || ^>= 0.11.0.0
     , containers           ^>= 0.6.2.1