diff --git a/CHANGELOG.md b/CHANGELOG.md
index 39b993c..4f2c566 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,9 @@
   necessarily depending on the newest version of the compiler. In addition
   to that Ormolu is now GHCJS-compatible.
 
+* Now unrecognized GHC options passed with `--ghc-opt` cause Ormolu to fail
+  (exit code 7).
+
 * Fixed formatting of result type in closed type families. See [issue
   420](https://github.com/tweag/ormolu/issues/420).
 
diff --git a/src/Ormolu.hs b/src/Ormolu.hs
index e4e5bac..600beec 100644
--- a/src/Ormolu.hs
+++ b/src/Ormolu.hs
@@ -51,11 +51,11 @@ ormolu ::
   String ->
   m Text
 ormolu cfg path str = do
-  (ws, result0) <-
+  (warnings, result0) <-
     parseModule' cfg OrmoluParsingFailed path str
   when (cfgDebug cfg) $ do
     traceM "warnings:\n"
-    traceM (concatMap showWarn ws)
+    traceM (concatMap showWarn warnings)
     traceM (prettyPrintParseResult result0)
   -- NOTE We're forcing 'txt' here because otherwise errors (such as
   -- messages about not-yet-supported functionality) will be thrown later
@@ -133,10 +133,10 @@ parseModule' ::
   String ->
   m ([GHC.Warn], ParseResult)
 parseModule' cfg mkException path str = do
-  (ws, r) <- parseModule cfg path str
+  (warnings, r) <- parseModule cfg path str
   case r of
     Left (spn, err) -> liftIO $ throwIO (mkException spn err)
-    Right x -> return (ws, x)
+    Right x -> return (warnings, x)
 
 -- | Pretty-print a 'GHC.Warn'.
 showWarn :: GHC.Warn -> String
diff --git a/src/Ormolu/Exception.hs b/src/Ormolu/Exception.hs
index 3bc88dd..6e8f8a2 100644
--- a/src/Ormolu/Exception.hs
+++ b/src/Ormolu/Exception.hs
@@ -8,6 +8,8 @@ module Ormolu.Exception
 where
 
 import Control.Exception
+import Data.List.NonEmpty (NonEmpty (..))
+import qualified Data.List.NonEmpty as NE
 import Data.Text (Text)
 import qualified GHC
 import Ormolu.Utils (showOutputable)
@@ -27,6 +29,8 @@ data OrmoluException
     OrmoluASTDiffers FilePath [GHC.SrcSpan]
   | -- | Formatted source code is not idempotent
     OrmoluNonIdempotentOutput GHC.RealSrcLoc Text Text
+  | -- | Some GHC options were not recognized
+    OrmoluUnrecognizedOpts (NonEmpty String)
   deriving (Eq, Show)
 
 instance Exception OrmoluException where
@@ -56,6 +60,11 @@ instance Exception OrmoluException where
         loc
         ["before: " ++ show left, "after:  " ++ show right]
         ++ "Please, consider reporting the bug.\n"
+    OrmoluUnrecognizedOpts opts ->
+      unlines
+        [ "The following GHC options were not recognized:",
+          (withIndent . unwords . NE.toList) opts
+        ]
 
 -- | Inside this wrapper 'OrmoluException' will be caught and displayed
 -- nicely using 'displayException'.
@@ -76,6 +85,7 @@ withPrettyOrmoluExceptions m = m `catch` h
           OrmoluOutputParsingFailed _ _ -> 4
           OrmoluASTDiffers _ _ -> 5
           OrmoluNonIdempotentOutput _ _ _ -> 6
+          OrmoluUnrecognizedOpts _ -> 7
 
 ----------------------------------------------------------------------------
 -- Helpers
diff --git a/src/Ormolu/Parser.hs b/src/Ormolu/Parser.hs
index 9c0a6b5..a82fd8e 100644
--- a/src/Ormolu/Parser.hs
+++ b/src/Ormolu/Parser.hs
@@ -15,6 +15,7 @@ import Control.Exception
 import Control.Monad
 import Control.Monad.IO.Class
 import Data.List ((\\), foldl', isPrefixOf)
+import qualified Data.List.NonEmpty as NE
 import Data.Maybe (catMaybes)
 import qualified DynFlags as GHC
 import DynFlags as GHC
@@ -57,8 +58,9 @@ parseModule Config {..} path input' = liftIO $ do
         GHC.setGeneralFlag'
           GHC.Opt_Haddock
           (setDefaultExts baseDynFlags)
+      extraOpts = dynOptionToLocatedStr <$> cfgDynOptions
   (warnings, dynFlags) <-
-    parsePragmasIntoDynFlags baseFlags path input' >>= \case
+    parsePragmasIntoDynFlags baseFlags extraOpts path input' >>= \case
       Right res -> pure res
       Left err ->
         let loc =
@@ -170,14 +172,24 @@ setDefaultExts flags = foldl' GHC.xopt_set flags autoExts
 -- More helpers (taken from HLint)
 
 parsePragmasIntoDynFlags ::
+  -- | Pre-set 'DynFlags'
   DynFlags ->
+  -- | Extra options (provided by user)
+  [Located String] ->
+  -- | File name (only for source location annotations)
   FilePath ->
+  -- | Input for parser
   String ->
   IO (Either String ([GHC.Warn], DynFlags))
-parsePragmasIntoDynFlags flags filepath str =
+parsePragmasIntoDynFlags flags extraOpts filepath str =
   catchErrors $ do
     let opts = GHC.getOptions flags (GHC.stringToStringBuffer str) filepath
-    (flags', _, warnings) <- parseDynamicFilePragma flags opts
+    (flags', leftovers, warnings) <-
+      parseDynamicFilePragma flags (opts <> extraOpts)
+    case NE.nonEmpty leftovers of
+      Nothing -> return ()
+      Just unrecognizedOpts ->
+        throwIO (OrmoluUnrecognizedOpts (unLoc <$> unrecognizedOpts))
     let flags'' = flags' `gopt_set` Opt_KeepRawTokenStream
     return $ Right (warnings, flags'')
   where