diff --git a/unix/asm_linux_s390x.s b/unix/asm_linux_s390x.s
index bdcf4124..11889859 100644
--- a/unix/asm_linux_s390x.s
+++ b/unix/asm_linux_s390x.s
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build s390x
+// +build linux
 // +build !gccgo
 
 #include "textflag.h"
diff --git a/unix/syscall_linux_s390x.go b/unix/syscall_linux_s390x.go
index a2485f70..3f98904e 100644
--- a/unix/syscall_linux_s390x.go
+++ b/unix/syscall_linux_s390x.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build s390x,linux
+
 package unix
 
 import (