diff --git a/src/internal/poll/fd_fsync_darwin.go b/src/internal/poll/fd_fsync_darwin.go
new file mode 100644
index 0000000000..23835f6e60
--- /dev/null
+++ b/src/internal/poll/fd_fsync_darwin.go
@@ -0,0 +1,23 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poll
+
+import "syscall"
+
+// Fsync invokes SYS_FCNTL with SYS_FULLFSYNC because
+// on OS X, SYS_FSYNC doesn't fully flush contents to disk.
+// See Issue #26650 as well as the man page for fsync on OS X.
+func (fd *FD) Fsync() error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	_, _, e1 := syscall.Syscall(syscall.SYS_FCNTL, uintptr(fd.Sysfd), syscall.F_FULLFSYNC, 0)
+	if e1 != 0 {
+		return e1
+	}
+	return nil
+}
diff --git a/src/internal/poll/fd_fsync_posix.go b/src/internal/poll/fd_fsync_posix.go
new file mode 100644
index 0000000000..943f59a9ab
--- /dev/null
+++ b/src/internal/poll/fd_fsync_posix.go
@@ -0,0 +1,18 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris windows
+
+package poll
+
+import "syscall"
+
+// Fsync wraps syscall.Fsync.
+func (fd *FD) Fsync() error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return syscall.Fsync(fd.Sysfd)
+}
diff --git a/src/internal/poll/fd_posix.go b/src/internal/poll/fd_posix.go
index f178a6fa0a..f899a74876 100644
--- a/src/internal/poll/fd_posix.go
+++ b/src/internal/poll/fd_posix.go
@@ -46,12 +46,3 @@ func (fd *FD) Ftruncate(size int64) error {
 	defer fd.decref()
 	return syscall.Ftruncate(fd.Sysfd, size)
 }
-
-// Fsync wraps syscall.Fsync.
-func (fd *FD) Fsync() error {
-	if err := fd.incref(); err != nil {
-		return err
-	}
-	defer fd.decref()
-	return syscall.Fsync(fd.Sysfd)
-}
diff --git a/src/syscall/syscall_darwin.go b/src/syscall/syscall_darwin.go
index 4d6aa4fcf2..98084a521c 100644
--- a/src/syscall/syscall_darwin.go
+++ b/src/syscall/syscall_darwin.go
@@ -252,6 +252,7 @@ func Kill(pid int, signum Signal) (err error) { return kill(pid, int(signum), 1)
 //sys	Fstat(fd int, stat *Stat_t) (err error) = SYS_FSTAT64
 //sys	Fstatfs(fd int, stat *Statfs_t) (err error) = SYS_FSTATFS64
 //sys	Fsync(fd int) (err error)
+//  Fsync is not called for os.File.Sync(). Please see internal/poll/fd_fsync_darwin.go
 //sys	Ftruncate(fd int, length int64) (err error)
 //sys	Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) = SYS_GETDIRENTRIES64
 //sys	Getdtablesize() (size int)