diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index 7d406c3973ba4944a4baee8363f59c736a98b52e..97bb150837df02422fc8a005d683cebb6191878f 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -39,7 +39,11 @@ void my_usr1(int sig, siginfo_t *si, void *u)
 	stack_t stk;
 	struct stk_data *p;
 
+#if __s390x__
+	register unsigned long sp asm("%15");
+#else
 	register unsigned long sp asm("sp");
+#endif
 
 	if (sp < (unsigned long)sstack ||
 			sp >= (unsigned long)sstack + SIGSTKSZ) {