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diff --git a/testsuite/tests/arityanal/should_run/T21694a.hs b/testsuite/tests/arityanal/should_run/T21694a.hs
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+++ b/testsuite/tests/arityanal/should_run/T21694a.hs
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+module Main (main) where
+
+import GHC.Exts
+import Control.DeepSeq
+import System.Exit
+
+-- If we eta expand the `False` branch will return
+-- a lambda \eta -> z instead of z.
+-- This behaves differently if the z argument is a bottom.
+-- We used to assume that a oneshot annotation would mean
+-- we could eta-expand on *all* branches. But this is clearly
+-- not sound in this case. So we test for this here.
+{-# NOINLINE f #-}
+f :: Bool -> (Int -> Int) -> Int -> Int
+f b z =
+    case b of
+        True -> oneShot $ \n -> n + 1
+        False -> z
+
+
+
+main :: IO Int
+main = do
+    return $! force $! f False (error "Urkh! But expected!")
+    return 0
+
+