diff --git a/hlint.cabal b/hlint.cabal
--- a/hlint.cabal
+++ b/hlint.cabal
@@ -1,7 +1,7 @@
 cabal-version:      >= 1.6
 build-type:         Simple
 name:               hlint
-version:            1.6.8
+version:            1.6.9
 license:            GPL
 license-file:       LICENSE
 category:           Development
diff --git a/src/Hint/Extensions.hs b/src/Hint/Extensions.hs
--- a/src/Hint/Extensions.hs
+++ b/src/Hint/Extensions.hs
@@ -12,6 +12,8 @@
 $(deriveNewtypes typeInfo)
 {-# LANGUAGE TemplateHaskell #-} \
 main = foo ''Bar
+{-# LANGUAGE PatternGuards #-} \
+test = case x of _ | y <- z -> w
 </TEST>
 -}
 
@@ -50,10 +52,12 @@
           f _ = False
 used ForeignFunctionInterface = hasT (un :: CallConv)
 used Generics = has isPExplTypeArg
-used PatternGuards = has f
-    where f (GuardedRhs _ [] _) = False
-          f (GuardedRhs _ [Qualifier _] _) = False
-          f _ = True
+used PatternGuards = has f1 & has f2
+    where f1 (GuardedRhs _ xs _) = g xs
+          f2 (GuardedAlt _ xs _) = g xs
+          g [] = False
+          g [Qualifier _] = False
+          g _ = True
 used StandaloneDeriving = has isDerivDecl
 used PatternSignatures = has isPatTypeSig
 used RecordWildCards = has isPFieldWildcard
diff --git a/src/Hint/Lambda.hs b/src/Hint/Lambda.hs
--- a/src/Hint/Lambda.hs
+++ b/src/Hint/Lambda.hs
@@ -31,6 +31,8 @@
 test = foo (\x -> y == x) -- (y ==)
 test = foo (\x -> x == g y) -- (== g y)
 test = foo (\x -> g x == x)
+cp i = show (i - 1)
+cp i = show (i + 1)
 </TEST>
 -}
 
@@ -96,8 +98,9 @@
 
 etaReduce :: Name -> Exp -> Maybe Exp
 etaReduce x (App y (Var (UnQual z))) | x == z && x `notElem` universeBi y = Just y
-etaReduce x (InfixApp y op z) | var x == y && x `notElem` universeBi z = Just $ RightSection op z
-                              | var x == z && x `notElem` universeBi y = Just $ LeftSection y op
+etaReduce x (InfixApp y op z) | goodOp && var x == y && x `notElem` universeBi z = Just $ RightSection op z
+                              | goodOp && var x == z && x `notElem` universeBi y = Just $ LeftSection y op
+    where goodOp = op `notElem` map (QVarOp . UnQual . Symbol . return) "+-"
 etaReduce x (App y z) | not (uglyEta y z) && x `notElem` universeBi y = do
     z2 <- etaReduce x z
     return $ InfixApp y (QVarOp $ UnQual $ Symbol ".") z2