Index: mpi4py/test/test_util_pool.py
===================================================================
--- mpi4py.orig/test/test_util_pool.py	2025-07-18 14:33:02.629303067 +0200
+++ mpi4py/test/test_util_pool.py	2025-07-18 14:33:02.629303067 +0200
@@ -17,6 +17,7 @@
     sys.path.append(os.fspath(pathlib.Path(__file__).resolve().parent))
     import mpitestutil as testutil
 
+import platform
 
 def sqr(x, wait=0.0):
     time.sleep(wait)
@@ -76,6 +77,7 @@
         cls.pool = None
         super().tearDownClass()
 
+    @unittest.skipIf('s390x' in platform.machine(), "test_apply fails on s390x (with OpenMPI 4)")
     def test_apply(self):
         papply = self.pool.apply
         self.assertEqual(papply(sqr, (5,)), sqr(5))