diff --git a/src/pkg/syscall/syscall_darwin.go b/src/pkg/syscall/syscall_darwin.go
index 1946ecd78ca..291ea557b0a 100644
--- a/src/pkg/syscall/syscall_darwin.go
+++ b/src/pkg/syscall/syscall_darwin.go
@@ -552,7 +552,7 @@ func Kill(pid int, signum int) (errno int) { return kill(pid, signum, 1) }
 //sys	Symlink(path string, link string) (errno int)
 //sys	Sync() (errno int)
 //sys	Truncate(path string, length int64) (errno int)
-//sys	Umask(newmask int) (errno int)
+//sys	Umask(newmask int) (oldmask int)
 //sys	Undelete(path string) (errno int)
 //sys	Unlink(path string) (errno int)
 //sys	Unmount(path string, flags int) (errno int)
diff --git a/src/pkg/syscall/syscall_freebsd.go b/src/pkg/syscall/syscall_freebsd.go
index 906955e9794..f5bb4541241 100644
--- a/src/pkg/syscall/syscall_freebsd.go
+++ b/src/pkg/syscall/syscall_freebsd.go
@@ -549,7 +549,7 @@ func SysctlUint32(name string) (value uint32, errno int) {
 //sys	Symlink(path string, link string) (errno int)
 //sys	Sync() (errno int)
 //sys	Truncate(path string, length int64) (errno int)
-//sys	Umask(newmask int) (errno int)
+//sys	Umask(newmask int) (oldmask int)
 //sys	Undelete(path string) (errno int)
 //sys	Unlink(path string) (errno int)
 //sys	Unmount(path string, flags int) (errno int)
diff --git a/src/pkg/syscall/zsyscall_darwin_386.go b/src/pkg/syscall/zsyscall_darwin_386.go
index 6442f078b3b..92525e3a80d 100644
--- a/src/pkg/syscall/zsyscall_darwin_386.go
+++ b/src/pkg/syscall/zsyscall_darwin_386.go
@@ -623,9 +623,9 @@ func Truncate(path string, length int64) (errno int) {
 	return
 }
 
-func Umask(newmask int) (errno int) {
-	_, _, e1 := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
-	errno = int(e1)
+func Umask(newmask int) (oldmask int) {
+	r0, _, _ := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
+	oldmask = int(r0)
 	return
 }
 
diff --git a/src/pkg/syscall/zsyscall_darwin_amd64.go b/src/pkg/syscall/zsyscall_darwin_amd64.go
index 5f4f9ee1d24..a0fc52c85ed 100644
--- a/src/pkg/syscall/zsyscall_darwin_amd64.go
+++ b/src/pkg/syscall/zsyscall_darwin_amd64.go
@@ -623,9 +623,9 @@ func Truncate(path string, length int64) (errno int) {
 	return
 }
 
-func Umask(newmask int) (errno int) {
-	_, _, e1 := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
-	errno = int(e1)
+func Umask(newmask int) (oldmask int) {
+	r0, _, _ := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
+	oldmask = int(r0)
 	return
 }
 
diff --git a/src/pkg/syscall/zsyscall_freebsd_386.go b/src/pkg/syscall/zsyscall_freebsd_386.go
index 9e165086a45..9e22134180c 100644
--- a/src/pkg/syscall/zsyscall_freebsd_386.go
+++ b/src/pkg/syscall/zsyscall_freebsd_386.go
@@ -623,9 +623,9 @@ func Truncate(path string, length int64) (errno int) {
 	return
 }
 
-func Umask(newmask int) (errno int) {
-	_, _, e1 := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
-	errno = int(e1)
+func Umask(newmask int) (oldmask int) {
+	r0, _, _ := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
+	oldmask = int(r0)
 	return
 }
 
diff --git a/src/pkg/syscall/zsyscall_freebsd_amd64.go b/src/pkg/syscall/zsyscall_freebsd_amd64.go
index f6d42bcd341..da67cdb829c 100644
--- a/src/pkg/syscall/zsyscall_freebsd_amd64.go
+++ b/src/pkg/syscall/zsyscall_freebsd_amd64.go
@@ -623,9 +623,9 @@ func Truncate(path string, length int64) (errno int) {
 	return
 }
 
-func Umask(newmask int) (errno int) {
-	_, _, e1 := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
-	errno = int(e1)
+func Umask(newmask int) (oldmask int) {
+	r0, _, _ := Syscall(SYS_UMASK, uintptr(newmask), 0, 0)
+	oldmask = int(r0)
 	return
 }