diff --git a/compiler/prelude/primops.txt.pp b/compiler/prelude/primops.txt.pp
index c16bc74de2a79849693e55e98a9f2b567d90fc44..8c936c6ac5736d06f000c6a6228849af035c1921 100644
--- a/compiler/prelude/primops.txt.pp
+++ b/compiler/prelude/primops.txt.pp
@@ -2019,9 +2019,11 @@ primop  RaiseOp "raise#" GenPrimOp
 -- must be *precise* - we don't want the strictness analyser turning
 -- one kind of bottom into another, as it is allowed to do in pure code.
 --
--- We currently produce topRes, which is much too conservative (interfering
--- with dead code elimination, unfortunately), but nothing else we currently
--- have on tap is actually correct.
+-- But we *do* want to know that it returns bottom after
+-- being applied to two arguments, so that this function is strict in y
+--     f x y | x>0       = raiseIO blah
+--           | y>0       = return 1
+--           | otherwise = return 2
 --
 -- TODO Check that the above notes on @f@ are valid. The function successfully
 -- produces an IO exception when compiled without optimization. If we analyze
@@ -2033,7 +2035,7 @@ primop  RaiseOp "raise#" GenPrimOp
 primop  RaiseIOOp "raiseIO#" GenPrimOp
    a -> State# RealWorld -> (# State# RealWorld, b #)
    with
-   strictness  = { \ _arity -> mkClosedStrictSig [topDmd, topDmd] topRes }
+   strictness  = { \ _arity -> mkClosedStrictSig [topDmd, topDmd] exnRes }
    out_of_line = True
    has_side_effects = True
 
diff --git a/testsuite/tests/stranal/should_run/all.T b/testsuite/tests/stranal/should_run/all.T
index a07900bbbc93fc8566af2f7a8600eb4d8e3a3b0f..076474608ef23845e9c68a922ed0e6633d000c04 100644
--- a/testsuite/tests/stranal/should_run/all.T
+++ b/testsuite/tests/stranal/should_run/all.T
@@ -14,4 +14,4 @@ test('T11076', normal, multimod_compile_and_run, ['T11076.hs', 'T11076_prim.cmm'
 test('T11555a', normal, compile_and_run, [''])
 test('T12368', exit_code(1), compile_and_run, [''])
 test('T12368a', exit_code(1), compile_and_run, [''])
-test('T13380', exit_code(1), compile_and_run, [''])
+test('T13380', [expect_broken(13380), exit_code(1)], compile_and_run, [''])