diff --git a/CHANGELOG.md b/CHANGELOG.md
index 147a9d10..8fffee36 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## next
+  - Exit with `exitFailure` on `AlreadyGeneratedByNewerHpack` or
+    `ExistingCabalFileWasModifiedManually` in `Hpack.printResult`
+
 ## Changes in 0.28.1
   - GHC 8.4.1 compatibility
 
diff --git a/src/Hpack.hs b/src/Hpack.hs
index f55920b2..3267ad92 100644
--- a/src/Hpack.hs
+++ b/src/Hpack.hs
@@ -139,6 +139,11 @@ printResult verbose r = do
       OutputUnchanged -> resultCabalFile r ++ " is up-to-date"
       AlreadyGeneratedByNewerHpack -> resultCabalFile r ++ " was generated with a newer version of hpack, please upgrade and try again."
       ExistingCabalFileWasModifiedManually -> resultCabalFile r ++ " was modified manually, please use --force to overwrite."
+  case resultStatus r of
+      Generated -> return ()
+      OutputUnchanged -> return ()
+      AlreadyGeneratedByNewerHpack -> exitFailure
+      ExistingCabalFileWasModifiedManually -> exitFailure
 
 printWarnings :: [String] -> IO ()
 printWarnings = mapM_ $ Utf8.hPutStrLn stderr . ("WARNING: " ++)