diff --git a/src/syscall/mkpost.go b/src/syscall/mkpost.go
index 26aeec843f..e75ba1502a 100644
--- a/src/syscall/mkpost.go
+++ b/src/syscall/mkpost.go
@@ -18,6 +18,7 @@ import (
 	"log"
 	"os"
 	"regexp"
+	"strings"
 )
 
 func main() {
@@ -38,10 +39,16 @@ func main() {
 		re = regexp.MustCompile("Pad_cgo[A-Za-z0-9_]*")
 		s = re.ReplaceAllString(s, "_")
 
+		// We want to keep X__val in Fsid. Hide it and restore it later.
+		s = strings.Replace(s, "X__val", "MKPOSTFSIDVAL", 1)
+
 		// Replace other unwanted fields with blank identifiers.
 		re = regexp.MustCompile("X_[A-Za-z0-9_]*")
 		s = re.ReplaceAllString(s, "_")
 
+		// Restore X__val in Fsid.
+		s = strings.Replace(s, "MKPOSTFSIDVAL", "X__val", 1)
+
 		// Force the type of RawSockaddr.Data to [14]int8 to match
 		// the existing gccgo API.
 		re = regexp.MustCompile("(Data\\s+\\[14\\])uint8")
diff --git a/src/syscall/ztypes_linux_s390x.go b/src/syscall/ztypes_linux_s390x.go
index cdde47863f..63c4a83b19 100644
--- a/src/syscall/ztypes_linux_s390x.go
+++ b/src/syscall/ztypes_linux_s390x.go
@@ -140,7 +140,7 @@ type Dirent struct {
 }
 
 type Fsid struct {
-	_ [2]int32
+	X__val [2]int32
 }
 
 type Flock_t struct {