diff --git a/macaw-semmc/src/Data/Macaw/SemMC/Generator.hs b/macaw-semmc/src/Data/Macaw/SemMC/Generator.hs
index d7c4aaaa..7db62406 100644
--- a/macaw-semmc/src/Data/Macaw/SemMC/Generator.hs
+++ b/macaw-semmc/src/Data/Macaw/SemMC/Generator.hs
@@ -52,6 +52,7 @@ import           GHC.TypeLits
 import           Control.Lens
 import qualified Control.Monad.Cont as Ct
 import qualified Control.Monad.Except as ET
+import           Control.Monad.Fail
 import qualified Control.Monad.Reader as Rd
 import           Control.Monad.ST ( ST )
 import qualified Control.Monad.State.Strict as St
@@ -248,6 +249,9 @@ instance St.MonadState (GenState arch ids s) (Generator arch ids s) where
 instance ET.MonadError GeneratorError (Generator arch ids s) where
   throwError e = Generator (Ct.ContT (\_ -> ET.throwError e))
 
+instance MonadFail (Generator arch ids s) where
+  fail err = ET.throwError $ GeneratorMessage $ show err
+
 -- | The type of continuations provided by 'shiftGen'
 type GenCont arch ids s a = a -> GenState arch ids s -> ET.ExceptT GeneratorError (ST s) (GenResult arch ids)