diff --git a/src-brittany/Main.hs b/src-brittany/Main.hs
index 4581adf..8bbd111 100644
--- a/src-brittany/Main.hs
+++ b/src-brittany/Main.hs
@@ -15,6 +15,11 @@ import qualified Language.Haskell.GHC.ExactPrint.Parsers as ExactPrint.Parsers
 import qualified Data.Map                                as Map
 import qualified Data.Monoid
 
+import           GHC                                      ( GenLocated(L) )
+import           Outputable                               ( Outputable(..)
+                                                          , showSDocUnsafe
+                                                          )
+
 import           Text.Read                                ( Read(..) )
 import qualified Text.ParserCombinators.ReadP            as ReadP
 import qualified Text.ParserCombinators.ReadPrec         as ReadPrec
@@ -384,8 +389,8 @@ coreIO putErrorLnIO config suppressOutput inputPathM outputPathM =
             uns@(ErrorUnknownNode{} : _) -> do
               putErrorLn $ "ERROR: encountered unknown syntactical constructs:"
               uns `forM_` \case
-                ErrorUnknownNode str ast -> do
-                  putErrorLn str
+                ErrorUnknownNode str ast@(L loc _) -> do
+                  putErrorLn $ str <> " at " <> showSDocUnsafe (ppr loc)
                   when
                       ( config
                       & _conf_debug
diff --git a/src/Language/Haskell/Brittany/Internal/LayouterBasics.hs b/src/Language/Haskell/Brittany/Internal/LayouterBasics.hs
index d5aac63..d4acb9f 100644
--- a/src/Language/Haskell/Brittany/Internal/LayouterBasics.hs
+++ b/src/Language/Haskell/Brittany/Internal/LayouterBasics.hs
@@ -694,7 +694,10 @@ docEnsureIndent
 docEnsureIndent ind mbd = mbd >>= \bd -> allocateNode $ BDFEnsureIndent ind bd
 
 unknownNodeError
-  :: Data.Data.Data ast => String -> ast -> ToBriDocM BriDocNumbered
+  :: Data.Data.Data ast
+  => String
+  -> GenLocated GHC.SrcSpan ast
+  -> ToBriDocM BriDocNumbered
 unknownNodeError infoStr ast = do
   mTell [ErrorUnknownNode infoStr ast]
   docLit $ Text.pack "{- BRITTANY ERROR UNHANDLED SYNTACTICAL CONSTRUCT -}"
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
index ee0596f..4d0440f 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
@@ -27,7 +27,7 @@ import           Language.Haskell.Brittany.Internal.ExactPrintUtils
 import           Language.Haskell.Brittany.Internal.Utils
 
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
-import           SrcLoc ( SrcSpan )
+import           SrcLoc ( SrcSpan, noSrcSpan )
 import           HsSyn
 import           Name
 import           BasicTypes ( InlinePragma(..)
@@ -202,20 +202,21 @@ layoutLocalBinds lbinds@(L _ binds) = case binds of
   -- x@(HsValBinds (ValBindsIn{})) ->
   --   Just . (:[]) <$> unknownNodeError "HsValBinds (ValBindsIn _ (_:_))" x
   HsValBinds (ValBindsIn bindlrs sigs) -> do
-    let
-      unordered
-        =  [ BagBind b | b <- Data.Foldable.toList bindlrs ]
-        ++ [ BagSig s | s <- sigs ]
-      ordered = sortBy (comparing bindOrSigtoSrcSpan) unordered
+    let unordered =
+          [ BagBind b | b <- Data.Foldable.toList bindlrs ]
+            ++ [ BagSig s | s <- sigs ]
+        ordered = sortBy (comparing bindOrSigtoSrcSpan) unordered
     docs <- docWrapNode lbinds $ join <$> ordered `forM` \case
       BagBind b -> either id return <$> layoutBind b
       BagSig  s -> return <$> layoutSig s
     return $ Just $ docs
   x@(HsValBinds (ValBindsOut _binds _lsigs)) ->
     -- i _think_ this case never occurs in non-processed ast
-    Just . (:[]) <$> unknownNodeError "HsValBinds ValBindsOut{}" x
-  x@(HsIPBinds _ipBinds) -> Just . (:[]) <$> unknownNodeError "HsIPBinds" x
-  EmptyLocalBinds        -> return $ Nothing
+    Just . (: []) <$> unknownNodeError "HsValBinds ValBindsOut{}"
+                                       (L noSrcSpan x)
+  x@(HsIPBinds _ipBinds) ->
+    Just . (: []) <$> unknownNodeError "HsIPBinds" (L noSrcSpan x)
+  EmptyLocalBinds -> return $ Nothing
 
 -- TODO: we don't need the `LHsExpr GhcPs` anymore, now that there is
 -- parSpacing stuff.B
diff --git a/src/Language/Haskell/Brittany/Internal/Types.hs b/src/Language/Haskell/Brittany/Internal/Types.hs
index ded4170..9358c2b 100644
--- a/src/Language/Haskell/Brittany/Internal/Types.hs
+++ b/src/Language/Haskell/Brittany/Internal/Types.hs
@@ -17,7 +17,7 @@ import qualified Language.Haskell.GHC.ExactPrint.Types as ExactPrint.Types
 
 import qualified Data.Text.Lazy.Builder as Text.Builder
 
-import           GHC ( Located, runGhc, GenLocated(L), moduleNameString, AnnKeywordId )
+import           GHC ( Located, runGhc, GenLocated(L), moduleNameString, AnnKeywordId, SrcSpan )
 
 import           Language.Haskell.GHC.ExactPrint ( AnnKey, Comment )
 import           Language.Haskell.GHC.ExactPrint.Types ( KeywordId, Anns, DeltaPos, mkAnnKey )
@@ -134,7 +134,7 @@ data BrittanyError
     --   output and second the corresponding, ill-formed input.
   | LayoutWarning String
     -- ^ some warning
-  | forall ast . Data.Data.Data ast => ErrorUnknownNode String ast
+  | forall ast . Data.Data.Data ast => ErrorUnknownNode String (GenLocated SrcSpan ast)
     -- ^ internal error: pretty-printing is not implemented for type of node
     --   in the syntax-tree
   | ErrorOutputCheck