diff --git a/protolude.cabal b/protolude.cabal
index 6e4fd5a76..08ed9d1c0 100644
--- a/protolude.cabal
+++ b/protolude.cabal
@@ -48,6 +48,7 @@ library
     Functor
     Semiring
     Bifunctor
+    Panic
 
   default-extensions:
     NoImplicitPrelude
diff --git a/src/Debug.hs b/src/Debug.hs
index d6cfcb2f3..dd7872657 100644
--- a/src/Debug.hs
+++ b/src/Debug.hs
@@ -18,10 +18,6 @@ import Control.Monad (Monad, return)
 import qualified Base as P
 import qualified Debug.Trace as T
 
-{-# WARNING undefined "'undefined' remains in code" #-}
-undefined :: a
-undefined = P.undefined
-
 {-# WARNING error "'error' remains in code" #-}
 error :: String -> a
 error = P.error
@@ -46,6 +42,8 @@ traceM s = T.trace s (return ())
 traceIO :: String -> P.IO ()
 traceIO = T.traceIO
 
-{-# WARNING notImplemented "'notImplemented' remains in code" #-}
 notImplemented :: a
 notImplemented = P.error "Not implemented"
+
+undefined :: a
+undefined = P.undefined
diff --git a/src/Panic.hs b/src/Panic.hs
new file mode 100644
index 000000000..fd7a2d5af
--- /dev/null
+++ b/src/Panic.hs
@@ -0,0 +1,17 @@
+module Panic (
+  FatalError(..),
+  panic,
+) where
+
+import Base (Show)
+import Data.Text(Text)
+import Control.Exception as X
+
+-- | Uncatchable exceptions thrown and never caught.
+data FatalError = FatalError { msg :: Text }
+  deriving (Show)
+
+instance Exception FatalError
+
+panic :: Text -> a
+panic a = throw (FatalError a)
diff --git a/src/Protolude.hs b/src/Protolude.hs
index 8a03b27f8..8ec142b5b 100644
--- a/src/Protolude.hs
+++ b/src/Protolude.hs
@@ -28,6 +28,7 @@ import Functor as X
 import Either as X
 import Applicative as X
 import Conv as X
+import Panic as X
 
 import Base as Base hiding (
     putStr