diff --git a/accelerate.cabal b/accelerate.cabal
index 1fd05af66..2c848ba01 100644
--- a/accelerate.cabal
+++ b/accelerate.cabal
@@ -329,6 +329,8 @@ library
         Data.Array.Accelerate.Data.Maybe
         Data.Array.Accelerate.Data.Monoid
         Data.Array.Accelerate.Data.Ratio
+        Data.Array.Accelerate.Debug.Assert
+        Data.Array.Accelerate.Debug.Error
         Data.Array.Accelerate.Debug.Trace
         Data.Array.Accelerate.Unsafe
 
diff --git a/src/Data/Array/Accelerate/AST.hs b/src/Data/Array/Accelerate/AST.hs
index 132170070..83366b167 100644
--- a/src/Data/Array/Accelerate/AST.hs
+++ b/src/Data/Array/Accelerate/AST.hs
@@ -286,6 +286,11 @@ data PreOpenAcc (acc :: Type -> Type -> Type) aenv a where
               -> acc             aenv arrs2
               -> PreOpenAcc  acc aenv arrs2
 
+  Aerror      :: ArraysR (arrs2)
+              -> Message              arrs1
+              -> acc             aenv arrs1
+              -> PreOpenAcc  acc aenv arrs2
+
   -- Array inlet. Triggers (possibly) asynchronous host->device transfer if
   -- necessary.
   --
@@ -768,6 +773,7 @@ instance HasArraysR acc => HasArraysR (PreOpenAcc acc) where
   arraysR (Apair as bs)               = TupRpair (arraysR as) (arraysR bs)
   arraysR Anil                        = TupRunit
   arraysR (Atrace _ _ bs)             = arraysR bs
+  arraysR (Aerror r _ _)              = r
   arraysR (Apply aR _ _)              = aR
   arraysR (Aforeign r _ _ _)          = r
   arraysR (Acond _ a _)               = arraysR a
@@ -992,6 +998,7 @@ rnfPreOpenAcc rnfA pacc =
     Apair as bs               -> rnfA as `seq` rnfA bs
     Anil                      -> ()
     Atrace msg as bs          -> rnfM msg `seq` rnfA as `seq` rnfA bs
+    Aerror repr msg as        -> rnfTupR rnfArrayR repr `seq` rnfM msg `seq` rnfA as
     Apply repr afun acc       -> rnfTupR rnfArrayR repr `seq` rnfAF afun `seq` rnfA acc
     Aforeign repr asm afun a  -> rnfTupR rnfArrayR repr `seq` rnf (strForeign asm) `seq` rnfAF afun `seq` rnfA a
     Acond p a1 a2             -> rnfE p `seq` rnfA a1 `seq` rnfA a2
@@ -1200,6 +1207,7 @@ liftPreOpenAcc liftA pacc =
     Apair as bs               -> [|| Apair $$(liftA as) $$(liftA bs) ||]
     Anil                      -> [|| Anil ||]
     Atrace msg as bs          -> [|| Atrace $$(liftMessage (arraysR as) msg) $$(liftA as) $$(liftA bs) ||]
+    Aerror repr msg as        -> [|| Aerror $$(liftArraysR repr) $$(liftMessage (arraysR as) msg) $$(liftA as) ||]
     Apply repr f a            -> [|| Apply $$(liftArraysR repr) $$(liftAF f) $$(liftA a) ||]
     Aforeign repr asm f a     -> [|| Aforeign $$(liftArraysR repr) $$(liftForeign asm) $$(liftPreOpenAfun liftA f) $$(liftA a) ||]
     Acond p t e               -> [|| Acond $$(liftE p) $$(liftA t) $$(liftA e) ||]
@@ -1396,6 +1404,7 @@ showPreAccOp Alet{}              = "Alet"
 showPreAccOp (Avar (Var _ ix))   = "Avar a" ++ show (idxToInt ix)
 showPreAccOp (Use aR a)          = "Use " ++ showArrayShort 5 (showsElt (arrayRtype aR)) aR a
 showPreAccOp Atrace{}            = "Atrace"
+showPreAccOp Aerror{}            = "Aerror"
 showPreAccOp Apply{}             = "Apply"
 showPreAccOp Aforeign{}          = "Aforeign"
 showPreAccOp Acond{}             = "Acond"
diff --git a/src/Data/Array/Accelerate/Analysis/Hash.hs b/src/Data/Array/Accelerate/Analysis/Hash.hs
index fc445ea00..09a022962 100644
--- a/src/Data/Array/Accelerate/Analysis/Hash.hs
+++ b/src/Data/Array/Accelerate/Analysis/Hash.hs
@@ -170,6 +170,7 @@ encodePreOpenAcc options encodeAcc pacc =
     Apair a1 a2                     -> intHost $(hashQ "Apair")       <> travA a1 <> travA a2
     Anil                            -> intHost $(hashQ "Anil")
     Atrace (Message _ _ msg) as bs  -> intHost $(hashQ "Atrace")      <> intHost (Hashable.hash msg) <> travA as <> travA bs
+    Aerror r (Message _ _ msg) as   -> intHost $(hashQ "Aerror")      <> encodeArraysType r <> intHost (Hashable.hash msg) <> travA as
     Apply _ f a                     -> intHost $(hashQ "Apply")       <> travAF f <> travA a
     Aforeign _ _ f a                -> intHost $(hashQ "Aforeign")    <> travAF f <> travA a
     Use repr a                      -> intHost $(hashQ "Use")         <> encodeArrayType repr <> deep (encodeArray a)
diff --git a/src/Data/Array/Accelerate/Debug/Assert.hs b/src/Data/Array/Accelerate/Debug/Assert.hs
new file mode 100644
index 000000000..fea839b6e
--- /dev/null
+++ b/src/Data/Array/Accelerate/Debug/Assert.hs
@@ -0,0 +1,122 @@
+{-# LANGUAGE AllowAmbiguousTypes   #-}
+{-# LANGUAGE FlexibleContexts      #-}
+{-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE ScopedTypeVariables   #-}
+{-# LANGUAGE TemplateHaskell       #-}
+{-# LANGUAGE TypeApplications      #-}
+{-# LANGUAGE TypeFamilies          #-}
+-- |
+-- Module      : Data.Array.Accelerate.Debug.Assert
+-- Copyright   : [2008..2020] The Accelerate Team
+-- License     : BSD3
+--
+-- Maintainer  : Trevor L. McDonell <trevor.mcdonell@gmail.com>
+-- Stability   : experimental
+-- Portability : non-portable (GHC extensions)
+--
+-- Functions for checking properties or invariants
+-- of a program.
+--
+-- @since 1.4.0.0
+--
+
+module Data.Array.Accelerate.Debug.Assert (
+
+  -- * Assertions
+  -- $assertions
+  --
+  assert, Assertion,
+  expEqual, AssertEqual,
+  arraysEqual, AssertArraysEqual,
+
+) where
+
+import qualified Data.Array.Accelerate                              as A
+import Data.Array.Accelerate.Smart
+import Data.Array.Accelerate.Sugar.Array                            as S
+import Data.Array.Accelerate.Sugar.Elt
+import qualified Data.Array.Accelerate.Representation.Array         as R
+import qualified Data.Array.Accelerate.Representation.Shape         as R
+
+
+-- $assertions
+--
+-- The 'assert' function verifies whether a predicate holds and will stop
+-- the execution of the array computation if the assertion does not hold.
+-- It will then also print the given error message to the console.
+--
+-- The predicate can be passed as a boolean expression ('Exp Bool'), but we
+-- have specialized assertions for array equivalence ('arraysEqual') and
+-- scalar equivalence ('expEqual').
+--
+
+-- Verifies whether the predicate holds, before the computation can continue
+-- with the result of the last argument. If the assertion does not hold,
+-- it will stop the array computation and print the error message.
+--
+assert :: forall a bs. (Assertion a bs, Arrays bs) => String -> a -> Acc bs -> Acc bs
+assert text assertion result
+  = A.acond (assertionCondition assertion result) result
+  $ Acc
+  $ SmartAcc
+  $ Aerror (S.arraysR @bs)
+           (assertionMessage @a @bs $ "Assertion failed: " ++ text)
+           arg
+  where
+    Acc arg = assertionArg assertion result
+
+class Arrays (AssertionArg a res) => Assertion a res where
+  type AssertionArg a res
+
+  assertionArg       :: a -> Acc res -> Acc (AssertionArg a res)
+  assertionMessage   :: String -> Message (ArraysR (AssertionArg a res))
+  assertionCondition :: a -> Acc res -> Exp Bool
+
+instance Assertion (Exp Bool) res where
+  type AssertionArg (Exp Bool) res = ()
+
+  assertionArg _ _ = Acc (SmartAcc Anil)
+  assertionMessage = Message (\_ -> "") (Just [|| \_ -> "" ||])
+  assertionCondition = const
+
+instance Assertion (Acc (Scalar Bool)) res where
+  type AssertionArg (Acc (Scalar Bool)) res = ()
+
+  assertionArg _ _ = Acc (SmartAcc Anil)
+  assertionMessage = Message (\_ -> "") (Just [|| \_ -> "" ||])
+  assertionCondition a _ = A.the a
+
+instance (Assertion a (), Show res, Arrays res) => Assertion (Acc res -> a) res where
+  type AssertionArg (Acc res -> a) res = res
+
+  assertionArg _ res = res
+  assertionMessage = Message  (\xs -> "\n" ++ show (toArr @res xs))
+                     (Just [||(\xs -> "\n" ++ show (toArr @res xs)) ||])
+  assertionCondition f res = assertionCondition (f res) (Acc (SmartAcc Anil) :: Acc ())
+
+data AssertEqual e = AssertEqual (Exp e) (Exp e)
+
+expEqual :: Exp e -> Exp e -> AssertEqual e
+expEqual = AssertEqual
+
+instance (Elt e, A.Eq e, Show e) => Assertion (AssertEqual e) res where
+  type AssertionArg (AssertEqual e) res = Scalar (e, e)
+
+  assertionArg (AssertEqual a b) _ = A.unit (A.T2 a b)
+  assertionMessage = Message  (\e -> let (a, b) = toElt @(e, e) (R.indexArray (R.ArrayR R.dim0 (eltR @(e, e))) e ()) in show a ++ " does not equal " ++ show b)
+                     (Just [||(\e -> let (a, b) = toElt @(e, e) (R.indexArray (R.ArrayR R.dim0 (eltR @(e, e))) e ()) in show a ++ " does not equal " ++ show b) ||])
+  assertionCondition (AssertEqual a b) _ = a A.== b
+
+data AssertArraysEqual as = AssertArraysEqual (Acc as) (Acc as)
+
+arraysEqual :: Acc as -> Acc as -> AssertArraysEqual as
+arraysEqual = AssertArraysEqual
+
+instance (Show sh, Show e, A.Shape sh, Elt e, A.Eq sh, A.Eq e) => Assertion (AssertArraysEqual (S.Array sh e)) res where
+  type AssertionArg (AssertArraysEqual (S.Array sh e)) res = (S.Array sh e, S.Array sh e)
+
+  assertionArg (AssertArraysEqual xs ys) _ = A.T2 xs ys
+  assertionMessage = Message  (\(((), xs), ys) -> "\n" ++ show (toArr @(S.Array sh e) xs) ++ "\ndoes not equal\n" ++ show (toArr @(S.Array sh e) ys))
+                     (Just [||(\(((), xs), ys) -> "\n" ++ show (toArr @(S.Array sh e) xs) ++ "\ndoes not equal\n" ++ show (toArr @(S.Array sh e) ys)) ||])
+  assertionCondition (AssertArraysEqual xs ys) _ = (A.shape xs A.== A.shape ys) A.&& A.the (A.all id $ A.reshape (A.I1 $ A.size xs) $ A.zipWith (A.==) xs ys)
diff --git a/src/Data/Array/Accelerate/Debug/Error.hs b/src/Data/Array/Accelerate/Debug/Error.hs
new file mode 100644
index 000000000..c506bd548
--- /dev/null
+++ b/src/Data/Array/Accelerate/Debug/Error.hs
@@ -0,0 +1,81 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TemplateHaskell     #-}
+{-# LANGUAGE TypeApplications    #-}
+-- |
+-- Module      : Data.Array.Accelerate.Debug.Error
+-- Copyright   : [2008..2020] The Accelerate Team
+-- License     : BSD3
+--
+-- Maintainer  : Trevor L. McDonell <trevor.mcdonell@gmail.com>
+-- Stability   : experimental
+-- Portability : non-portable (GHC extensions)
+--
+-- Functions for checking properties or invariants
+-- of a program.
+--
+-- @since 1.4.0.0
+--
+
+module Data.Array.Accelerate.Debug.Error (
+
+  -- * Throwing errors
+  -- $errors
+  --
+  aerror, aerrorArray, aerrorExp
+
+) where
+
+import Data.Array.Accelerate.Language
+import Data.Array.Accelerate.Smart
+import Data.Array.Accelerate.Sugar.Array                            as S
+import Data.Array.Accelerate.Sugar.Elt
+import qualified Data.Array.Accelerate.Representation.Array         as R
+import qualified Data.Array.Accelerate.Representation.Shape         as R
+
+
+-- $errors
+--
+-- The 'aerror', 'aerrorArray', and 'aerrorExp' functions abort the execution
+-- of the array program and print errors to an output stream. They are intended
+-- for stopping the program when the program is in some invalid state, which
+-- was expected to be unreachable.
+--
+-- Besides printing a given error message, it can also print the contents of an
+-- array (with 'aerrorArray') or print some scalar value ('aerrorExp').
+--
+
+-- | Stops execution of the array computation and outputs the error message to
+-- the console.
+--
+aerror :: forall a. Arrays a => String -> Acc a
+aerror message
+  = Acc
+  $ SmartAcc
+  $ Aerror (S.arraysR @a)
+           (Message (\_ -> "") (Just [|| \_ -> "" ||]) message)
+           (SmartAcc Anil :: SmartAcc ())
+
+-- | Outputs the trace message and the array(s) from the second argument to
+-- the console, before the 'Acc' computation proceeds with the result of
+-- the third argument.
+--
+aerrorArray :: forall a b. (Arrays a, Arrays b, Show a) => String -> Acc a -> Acc b
+aerrorArray message (Acc inspect)
+  = Acc
+  $ SmartAcc
+  $ Aerror (S.arraysR @b)
+           (Message (show . toArr @a)
+           (Just [|| show . toArr @a ||]) message) inspect
+
+-- | Outputs the trace message and a scalar value to the console, before
+-- the 'Acc' computation proceeds with the result of the third argument.
+--
+aerrorExp :: forall e a. (Elt e, Show e, Arrays a) => String -> Exp e -> Acc a
+aerrorExp message value =
+  let Acc inspect = unit value
+   in Acc
+    $ SmartAcc
+    $ Aerror (S.arraysR @a)
+             (Message (\a -> show (toElt @e (R.indexArray (R.ArrayR R.dim0 (eltR @e)) a ())))
+             (Just [|| \a -> show (toElt @e (R.indexArray (R.ArrayR R.dim0 (eltR @e)) a ())) ||]) message) inspect
+
diff --git a/src/Data/Array/Accelerate/Interpreter.hs b/src/Data/Array/Accelerate/Interpreter.hs
index d10b99724..f9d28b217 100644
--- a/src/Data/Array/Accelerate/Interpreter.hs
+++ b/src/Data/Array/Accelerate/Interpreter.hs
@@ -36,7 +36,7 @@ module Data.Array.Accelerate.Interpreter (
   run, run1, runN,
 
   -- Internal (hidden)
-  evalPrim, evalPrimConst, evalCoerceScalar, atraceOp,
+  evalPrim, evalPrimConst, evalCoerceScalar, atraceOp, aerrorOp,
 
 ) where
 
@@ -210,6 +210,7 @@ evalOpenAcc (AST.Manifest pacc) aenv =
                                      (TupRpair r1 r2, (a1, a2))
     Anil                          -> (TupRunit, ())
     Atrace msg as bs              -> unsafePerformIO $ manifest bs <$ atraceOp msg (snd $ manifest as)
+    Aerror _ msg as               -> aerrorOp msg $ snd $ manifest as
     Apply repr afun acc           -> (repr, evalOpenAfun afun aenv $ snd $ manifest acc)
     Aforeign repr _ afun acc      -> (repr, evalOpenAfun afun Empty $ snd $ manifest acc)
     Acond p acc1 acc2
@@ -874,6 +875,12 @@ atraceOp (Message show _ msg) as =
          then traceIO msg
          else traceIO $ printf "%s: %s" msg str
 
+aerrorOp :: Message as -> as -> bs
+aerrorOp (Message show _ msg) as =
+  let str = show as
+   in if null str
+         then error msg
+         else error $ printf "%s: %s" msg str
 
 -- Scalar expression evaluation
 -- ----------------------------
diff --git a/src/Data/Array/Accelerate/Pretty/Graphviz.hs b/src/Data/Array/Accelerate/Pretty/Graphviz.hs
index f03dfeb3b..51c5b9a41 100644
--- a/src/Data/Array/Accelerate/Pretty/Graphviz.hs
+++ b/src/Data/Array/Accelerate/Pretty/Graphviz.hs
@@ -230,6 +230,7 @@ prettyDelayedOpenAcc detail ctx aenv atop@(Manifest pacc) =
 
     Anil                            -> "()"             .$ []
     Atrace (Message _ _ msg) as bs  -> "atrace"         .$ [ return $ PDoc (fromString msg) [], ppA as, ppA bs ]
+    Aerror _ (Message _ _ msg) as   -> "aerror"         .$ [ return $ PDoc (fromString msg) [], ppA as ]
     Use repr arr                    -> "use"            .$ [ return $ PDoc (prettyArray repr arr) [] ]
     Unit _ e                        -> "unit"           .$ [ ppE e ]
     Generate _ sh f                 -> "generate"       .$ [ ppE sh, ppF f ]
diff --git a/src/Data/Array/Accelerate/Pretty/Print.hs b/src/Data/Array/Accelerate/Pretty/Print.hs
index bb8ebbe9e..913276512 100644
--- a/src/Data/Array/Accelerate/Pretty/Print.hs
+++ b/src/Data/Array/Accelerate/Pretty/Print.hs
@@ -194,6 +194,7 @@ prettyPreOpenAcc config ctx prettyAcc extractAcc aenv pacc =
 
 
     Atrace (Message _ _ msg) as bs  -> ppN "atrace"      .$ [ fromString (show msg), ppA as, ppA bs ]
+    Aerror _ (Message _ _ msg) as   -> ppN "aerror"      .$ [ fromString (show msg), ppA as ]
     Aforeign _ ff _ a               -> ppN "aforeign"    .$ [ pretty (strForeign ff), ppA a ]
     Awhile p f a                    -> ppN "awhile"      .$ [ ppAF p, ppAF f, ppA a ]
     Use repr arr                    -> ppN "use"         .$ [ prettyArray repr arr ]
diff --git a/src/Data/Array/Accelerate/Smart.hs b/src/Data/Array/Accelerate/Smart.hs
index 249a1e18b..ed12823b5 100644
--- a/src/Data/Array/Accelerate/Smart.hs
+++ b/src/Data/Array/Accelerate/Smart.hs
@@ -359,6 +359,11 @@ data PreSmartAcc acc exp as where
                 -> acc arrs2
                 -> PreSmartAcc acc exp arrs2
 
+  Aerror        :: ArraysR arrs2
+                -> Message arrs1
+                -> acc arrs1
+                -> PreSmartAcc acc exp arrs2
+
   Use           :: ArrayR (Array sh e)
                 -> Array sh e
                 -> PreSmartAcc acc exp (Array sh e)
@@ -805,6 +810,7 @@ instance HasArraysR acc => HasArraysR (PreSmartAcc acc exp) where
                                    PairIdxRight -> t2
     Aprj _ _                  -> error "Ejector seat? You're joking!"
     Atrace _ _ a              -> arraysR a
+    Aerror repr _ _           -> repr
     Use repr _                -> TupRsingle repr
     Unit tp _                 -> TupRsingle $ ArrayR ShapeRz $ tp
     Generate repr _ _         -> TupRsingle repr
@@ -1315,6 +1321,7 @@ showPreAccOp Apair{}               = "Apair"
 showPreAccOp Anil{}                = "Anil"
 showPreAccOp Aprj{}                = "Aprj"
 showPreAccOp Atrace{}              = "Atrace"
+showPreAccOp Aerror{}              = "Aerror"
 showPreAccOp Unit{}                = "Unit"
 showPreAccOp Generate{}            = "Generate"
 showPreAccOp Reshape{}             = "Reshape"
diff --git a/src/Data/Array/Accelerate/Trafo/Fusion.hs b/src/Data/Array/Accelerate/Trafo/Fusion.hs
index 81487be09..32622280a 100644
--- a/src/Data/Array/Accelerate/Trafo/Fusion.hs
+++ b/src/Data/Array/Accelerate/Trafo/Fusion.hs
@@ -178,6 +178,7 @@ manifest config (OpenAcc pacc) =
     Apair a1 a2             -> Apair (manifest config a1) (manifest config a2)
     Anil                    -> Anil
     Atrace msg a1 a2        -> Atrace msg (manifest config a1) (manifest config a2)
+    Aerror repr msg a1      -> Aerror repr msg (manifest config a1)
     Apply repr f a          -> apply repr (cvtAF f) (manifest config a)
     Aforeign repr ff f a    -> Aforeign repr ff (cvtAF f) (manifest config a)
 
@@ -370,6 +371,7 @@ embedPreOpenAcc config matchAcc embedAcc elimAcc pacc
     Awhile p f a        -> done $ Awhile (cvtAF p) (cvtAF f) (cvtA a)
     Apair a1 a2         -> done $ Apair (cvtA a1) (cvtA a2)
     Atrace msg a1 a2    -> done $ Atrace msg (cvtA a1) (cvtA a2)
+    Aerror repr msg a1  -> done $ Aerror repr msg (cvtA a1)
     Aforeign aR ff f a  -> done $ Aforeign aR ff (cvtAF f) (cvtA a)
     -- Collect s           -> collectD s
 
@@ -1548,6 +1550,7 @@ aletD' embedAcc elimAcc (LeftHandSideSingle ArrayR{}) (Embed env1 cc1) (Embed en
         Acond p at ae           -> Acond (cvtE p) (cvtA at) (cvtA ae)
         Anil                    -> Anil
         Atrace msg a b          -> Atrace msg (cvtA a) (cvtA b)
+        Aerror repr msg a       -> Aerror repr msg (cvtA a)
         Apair a1 a2             -> Apair (cvtA a1) (cvtA a2)
         Awhile p f a            -> Awhile (cvtAF p) (cvtAF f) (cvtA a)
         Apply repr f a          -> Apply repr (cvtAF f) (cvtA a)
diff --git a/src/Data/Array/Accelerate/Trafo/LetSplit.hs b/src/Data/Array/Accelerate/Trafo/LetSplit.hs
index 900c14850..86d18b999 100644
--- a/src/Data/Array/Accelerate/Trafo/LetSplit.hs
+++ b/src/Data/Array/Accelerate/Trafo/LetSplit.hs
@@ -38,6 +38,7 @@ convertPreOpenAcc = \case
   Apair a1 a2                     -> Apair (convertAcc a1) (convertAcc a2)
   Anil                            -> Anil
   Atrace msg as bs                -> Atrace msg (convertAcc as) (convertAcc bs)
+  Aerror repr msg as              -> Aerror repr msg (convertAcc as)
   Apply repr f a                  -> Apply repr (convertAfun f) (convertAcc a)
   Aforeign repr asm f a           -> Aforeign repr asm (convertAfun f) (convertAcc a)
   Acond e a1 a2                   -> Acond e (convertAcc a1) (convertAcc a2)
diff --git a/src/Data/Array/Accelerate/Trafo/Sharing.hs b/src/Data/Array/Accelerate/Trafo/Sharing.hs
index bd276081b..755ac7605 100644
--- a/src/Data/Array/Accelerate/Trafo/Sharing.hs
+++ b/src/Data/Array/Accelerate/Trafo/Sharing.hs
@@ -340,6 +340,7 @@ convertSharingAcc config alyt aenv (ScopedAcc lams (AccSharing _ preAcc))
       Aprj ix a                   -> let AST.OpenAcc a' = cvtAprj ix a
                                      in a'
       Atrace msg acc1 acc2        -> AST.Atrace msg (cvtA acc1) (cvtA acc2)
+      Aerror repr msg acc1        -> AST.Aerror repr msg (cvtA acc1)
       Use repr array              -> AST.Use repr array
       Unit tp e                   -> AST.Unit tp (cvtE e)
       Generate repr@(ArrayR shr _) sh f
@@ -1507,6 +1508,9 @@ makeOccMapSharingAcc config accOccMap = traverseAcc
                                              (a', h1) <- traverseAcc lvl acc1
                                              (b', h2) <- traverseAcc lvl acc2
                                              return (Atrace msg a' b', h1 `max` h2 + 1)
+            Aerror repr msg acc1        -> do
+                                             (a', h1) <- traverseAcc lvl acc1
+                                             return (Aerror repr msg a', h1 + 1)
             Use repr arr                -> return (Use repr arr, 1)
             Unit tp e                   -> do
                                              (e', h) <- traverseExp lvl e
@@ -2368,6 +2372,10 @@ determineScopesSharingAcc config accOccMap = scopesAcc
                                        (a2', accCount2) = scopesAcc a2
                                      in
                                        reconstruct (Atrace msg a1' a2') (accCount1 +++ accCount2)
+          Aerror repr msg a1      -> let
+                                       (a1', accCount1) = scopesAcc a1
+                                     in
+                                       reconstruct (Aerror repr msg a1') accCount1
           Use repr arr            -> reconstruct (Use repr arr) noNodeCounts
           Unit tp e               -> let
                                        (e', accCount) = scopesExp e
diff --git a/src/Data/Array/Accelerate/Trafo/Shrink.hs b/src/Data/Array/Accelerate/Trafo/Shrink.hs
index 574747865..7b99de0a4 100644
--- a/src/Data/Array/Accelerate/Trafo/Shrink.hs
+++ b/src/Data/Array/Accelerate/Trafo/Shrink.hs
@@ -544,6 +544,7 @@ usesOfPreAcc withShape countAcc idx = count
       Apair a1 a2                -> countA a1 + countA a2
       Anil                       -> 0
       Atrace _ a1 a2             -> countA a1 + countA a2
+      Aerror _ _ a1              -> countA a1
       Apply _ f a                -> countAF f idx + countA a
       Aforeign _ _ _ a           -> countA a
       Acond p t e                -> countE p + countA t + countA e
diff --git a/src/Data/Array/Accelerate/Trafo/Substitution.hs b/src/Data/Array/Accelerate/Trafo/Substitution.hs
index ccb794555..5485bbfca 100644
--- a/src/Data/Array/Accelerate/Trafo/Substitution.hs
+++ b/src/Data/Array/Accelerate/Trafo/Substitution.hs
@@ -681,6 +681,7 @@ rebuildPreOpenAcc k av acc =
     Apair as bs               -> Apair           <$> k av as <*> k av bs
     Anil                      -> pure Anil
     Atrace msg as bs          -> Atrace msg      <$> k av as <*> k av bs
+    Aerror repr msg as        -> Aerror repr msg <$> k av as
     Apply repr f a            -> Apply repr      <$> rebuildAfun k av f <*> k av a
     Acond p t e               -> Acond           <$> rebuildOpenExp (pure . IE) av' p <*> k av t <*> k av e
     Awhile p f a              -> Awhile          <$> rebuildAfun k av p <*> rebuildAfun k av f <*> k av a