diff --git a/compiler/stranal/WwLib.hs b/compiler/stranal/WwLib.hs
index ab0a4d1ee19be7f06214296046a227aed83feef1..040a6d7da97f9790920885469f53d38a76559670 100644
--- a/compiler/stranal/WwLib.hs
+++ b/compiler/stranal/WwLib.hs
@@ -269,11 +269,21 @@ mkWorkerArgs dflags args res_ty
     | otherwise
     = (args ++ [voidArgId], args ++ [voidPrimId])
     where
+      -- See "Making wrapper args" section above
       needsAValueLambda =
-        isUnliftedType res_ty
+        lifted
+        -- We may encounter a levity-polymorphic result, in which case we
+        -- conservatively assume that we have laziness that needs preservation.
+        -- See #15186.
         || not (gopt Opt_FunToThunk dflags)
            -- see Note [Protecting the last value argument]
 
+      -- Might the result be lifted?
+      lifted =
+        case isLiftedType_maybe res_ty of
+          Just lifted -> lifted
+          Nothing     -> True
+
 {-
 Note [Protecting the last value argument]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/testsuite/tests/simplCore/should_compile/all.T b/testsuite/tests/simplCore/should_compile/all.T
index a430521c89ffd30749a9c2d15a4efafb7705f5f4..5ad7dba94a163d15fb1b846173ac438c53fe78ab 100644
--- a/testsuite/tests/simplCore/should_compile/all.T
+++ b/testsuite/tests/simplCore/should_compile/all.T
@@ -315,4 +315,4 @@ test('T15002', [ req_profiling ], compile, ['-O -fprof-auto -prof'])
 test('T15005', normal, compile, ['-O'])
 # we omit profiling because it affects the optimiser and makes the test fail
 test('T15056', [extra_files(['T15056a.hs']), omit_ways(['profasm'])], multimod_compile, ['T15056', '-O -v0 -ddump-rule-firings'])
-test('T15186', expect_broken(15186), multimod_compile, ['T15186', '-v0'])
+test('T15186', normal, multimod_compile, ['T15186', '-v0'])