diff --git a/Debug/Trace/LocationTH.hs b/Debug/Trace/LocationTH.hs
--- a/Debug/Trace/LocationTH.hs
+++ b/Debug/Trace/LocationTH.hs
@@ -10,7 +10,7 @@
 -- This module provides a Template Haskell based mechanism to tag failures
 -- with the location of the failure call. The location message includes the
 -- file name, line and column numbers.
--- 
+--
 
 {-# LANGUAGE TemplateHaskell #-}
 module Debug.Trace.LocationTH
@@ -20,6 +20,8 @@
     , undef
     , check
     , checkIO
+    , checkTrace
+    , checkTraceIO
     ) where
 
 import qualified Control.Exception as C
@@ -27,6 +29,7 @@
 import Language.Haskell.TH.Ppr (pprint)
 import Language.Haskell.TH.Syntax (location, Loc(..), Q, Exp, lift)
 import System.IO.Unsafe  (unsafePerformIO)
+import qualified Text.PrettyPrint.HughesPJ as PP
 import Text.PrettyPrint.HughesPJ
 
 ppUnless :: Bool -> Doc -> Doc
@@ -39,16 +42,16 @@
             , loc_start = (sline, start_col)
             , loc_end = (eline, end_col) })
     | sline == eline = hcat
-        [ text src_path <> colon
+        [ text src_path PP.<> colon
         , int sline, char ':', int start_col
         , ppUnless (end_col - start_col <= 1)
-                   (char '-' <> int (end_col-1))
+                   (char '-' PP.<> int (end_col-1))
         ]
     | otherwise = hcat
-        [ text src_path <> colon
-        , parens (int sline <> char ',' <>  int start_col)
+        [ text src_path PP.<> colon
+        , parens (int sline PP.<> char ',' PP.<>  int start_col)
         , char '-'
-        , parens (int eline <> char ',' <>
+        , parens (int eline PP.<> char ',' PP.<>
             if end_col == 0 then int end_col else int (end_col-1))
         ]
 
@@ -57,7 +60,7 @@
 --
 -- @$__LOCATION__ :: 'String'@
 --
--- >>> $__LOCATION__ 
+-- >>> $__LOCATION__
 -- "<interactive>:1:1-13"
 --
 __LOCATION__ :: Q Exp
@@ -66,7 +69,7 @@
 --
 -- | If the first argument evaluates to 'True', then the result is the second
 -- argument. Otherwise an 'AssertionFailed' exception is raised, containing a
--- 'String' with the source file and line number of the call to 'assert'. 
+-- 'String' with the source file and line number of the call to 'assert'.
 --
 -- @$(assert [| 'False' |]) :: a -> a@
 --
@@ -76,13 +79,13 @@
 assert :: Q Exp -> Q Exp
 assert t = do
     st <- pprint `fmap` t
-    [|
-        \cont -> if not $t
-            then throw $ AssertionFailed $
-                $__LOCATION__ ++ ": Assertion `" ++ st ++ "' failed"
-            else cont
-     |]
+    [| assert' $t $__LOCATION__ st |]
 
+assert' :: Bool -> String -> String -> a -> a
+assert' False loc st _ = throw $ AssertionFailed $
+    loc ++ ": Assertion `" ++ st ++ "' failed"
+assert' True  _   _  x = x
+
 --
 -- | A location-emitting 'error' call.
 --
@@ -92,8 +95,11 @@
 -- *** Exception: <interactive>:1:1-8: no such thing.
 --
 failure :: Q Exp
-failure = [| \t -> error $ $__LOCATION__ ++ ": " ++ t |]
+failure = [| failure' $__LOCATION__ |]
 
+failure' :: String -> String -> a
+failure' loc t = error $ loc ++ ": " ++ t
+
 --
 -- | A location-emitting 'undefined'.
 --
@@ -112,7 +118,7 @@
 -- message.
 --
 -- @$check :: c -> c@
--- 
+--
 -- >>> $check $ head []
 -- *** Exception: <interactive>:1:1-6: Prelude.head: empty list
 --
@@ -121,6 +127,8 @@
 --
 -- >>> $check $ Just $ head ""
 -- Just *** Exception: Prelude.head: empty list
+-- >>> Just $ $check $ head ""
+-- Just *** Exception: <interactive>:9:8-13: Prelude.head: empty list
 -- >>> $check $ join deepseq $ Just $ head ""
 -- *** Exception: <interactive>:1:1-6: Prelude.head: empty list
 --
@@ -138,7 +146,40 @@
 -- "*** Exception: <interactive>:1:1-8: /foo: openFile: does not exist (No such file or directory)
 --
 checkIO :: Q Exp
-checkIO = [| \a -> C.catch a $ \e -> return $ $failure (showEx e) |]
+checkIO = [| checkIO' $__LOCATION__ |]
+
+checkIO' :: String -> IO a -> IO a
+checkIO' loc a = C.catch a $ \e -> return $ failure' loc (showEx e)
+
+--
+-- | 'checkTrace' extends 'check' with the ability to add a custom string
+-- to the error message.
+--
+-- @$checkTrace :: String -> c -> c@
+--
+-- >>> $checkTrace "XXX" $ head []
+-- *** Exception: <interactive>:1:1-6 XXX: Prelude.head: empty list
+--
+checkTrace :: Q Exp
+checkTrace = [| checkTrace' $__LOCATION__ |]
+
+checkTrace' :: String -> String -> a -> a
+checkTrace' loc t = unsafePerformIO . checkTraceIO' loc t . C.evaluate
+
+--
+-- | 'checkTraceIO' extends 'checkIO' with the ability to add a custom
+-- string to the error message.
+--
+-- @$checkTraceIO :: String -> IO a -> IO a@
+--
+-- >>> $checkTraceIO "XXX" $ readFile "/foo"
+-- "*** Exception: <interactive>:1:1-8 XXX: /foo: openFile: does not exist (No such file or directory)
+--
+checkTraceIO :: Q Exp
+checkTraceIO = [| checkTraceIO' $__LOCATION__ |]
+
+checkTraceIO' :: String -> String -> IO a -> IO a
+checkTraceIO' loc t = checkIO' (loc ++ " " ++ t)
 
 showEx :: C.SomeException -> String
 showEx = show
diff --git a/loch-th.cabal b/loch-th.cabal
--- a/loch-th.cabal
+++ b/loch-th.cabal
@@ -1,10 +1,10 @@
 Name:                loch-th
-Version:             0.1
+Version:             0.2.2
 Synopsis:            Support for precise error locations in source files (Template Haskell version)
 Description:         This module provides a Template Haskell based mechanism to
-		     tag failures with the location of the failure call. The
-		     location message includes the file name, line and column
-		     numbers.
+                     tag failures with the location of the failure call. The
+                     location message includes the file name, line and column
+                     numbers.
 Homepage:            https://github.com/liskin/loch-th
 License:             BSD3
 License-file:        LICENSE
@@ -12,8 +12,8 @@
 Maintainer:          tomi@nomi.cz
 Category:            Development
 Build-type:          Simple
-Cabal-version:       >=1.2
+Cabal-version:       >=1.6
 
 Library
   Exposed-modules:     Debug.Trace.LocationTH
-  Build-depends:       base >=4 && <5, template-haskell, pretty
+  Build-depends:       base == 4.*, template-haskell, pretty