diff --git a/src/validate-whitespace.hs b/src/validate-whitespace.hs
index 5fbd46b..e5799f2 100644
--- a/src/validate-whitespace.hs
+++ b/src/validate-whitespace.hs
@@ -22,7 +22,7 @@ import           Common
 hasSuffix :: Text -> Bool
 hasSuffix fn = any (`T.isSuffixOf` fn) suffixes
   where
-    suffixes = T.words ".hs .hsc .lhs .cabal .c .h .lhs-boot .hs-boot .x .y"
+    suffixes = T.words ".hs .hsc .lhs .cabal .c .h .lhs-boot .hs-boot .x .y .stdout .stderr"
 
 main :: IO ()
 main = do
@@ -98,6 +98,10 @@ lintBlob blobs0 blob1 = execWriter $ do
         tell [ LintMsg LintLvlErr lno l "introduces trailing whitespace"
              | (lno,l) <- zip [1..] lns, hasTrail l ]
 
+    when (hasCRLF blob1 && not (any hasCRLF blobs0)) $ do
+        tell [ LintMsg LintLvlErr lno l "introduces Windows line ending"
+             | (lno,l) <- zip [1..] lns, hasCRLF l ]
+
     when (missingFinalEOL blob1) $ if not (any missingFinalEOL blobs0)
           then tell [LintMsg LintLvlErr  llno lln "lacking final EOL"]
           else tell [LintMsg LintLvlWarn llno lln "lacking final EOL"]
@@ -120,6 +124,9 @@ lintBlob blobs0 blob1 = execWriter $ do
                     , "\t"     `T.isSuffixOf` t
                     ]
 
+    hasCRLF :: Text -> Bool
+    hasCRLF t = "\r\n" `T.isInfixOf` t || "\r" `T.isSuffixOf` t
+
     missingFinalEOL :: Text -> Bool
     missingFinalEOL = not . T.isSuffixOf "\n"