diff --git a/Cargo.toml b/Cargo.toml
index 9b55abe5c..bf11e66fa 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -347,6 +347,7 @@ tempfile = "= 3.1.0"
 time = "0.1"
 unindent = "0.1"
 uucore = { version=">=0.0.7", package="uucore", path="src/uucore", features=["entries"] }
+walkdir = "2.2"
 
 [target.'cfg(unix)'.dev-dependencies]
 rust-users = { version="0.10", package="users" }
diff --git a/src/uu/cp/src/cp.rs b/src/uu/cp/src/cp.rs
index 0922af241..01ad4a8aa 100644
--- a/src/uu/cp/src/cp.rs
+++ b/src/uu/cp/src/cp.rs
@@ -431,6 +431,10 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         .arg(Arg::with_name(OPT_NO_DEREFERENCE_PRESERVE_LINKS)
              .short("d")
              .help("same as --no-dereference --preserve=links"))
+        .arg(Arg::with_name(OPT_ONE_FILE_SYSTEM)
+             .short("x")
+             .long(OPT_ONE_FILE_SYSTEM)
+             .help("stay on this file system"))
 
         // TODO: implement the following args
         .arg(Arg::with_name(OPT_COPY_CONTENTS)
@@ -442,10 +446,6 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
              .takes_value(true)
              .value_name("WHEN")
              .help("NotImplemented: control creation of sparse files. See below"))
-        .arg(Arg::with_name(OPT_ONE_FILE_SYSTEM)
-             .short("x")
-             .long(OPT_ONE_FILE_SYSTEM)
-             .help("NotImplemented: stay on this file system"))
         .arg(Arg::with_name(OPT_CONTEXT)
              .long(OPT_CONTEXT)
              .takes_value(true)
@@ -563,6 +563,7 @@ impl Options {
         let not_implemented_opts = vec![
             OPT_COPY_CONTENTS,
             OPT_SPARSE,
+            #[cfg(not(any(windows, unix)))]
             OPT_ONE_FILE_SYSTEM,
             OPT_CONTEXT,
             #[cfg(windows)]
@@ -937,7 +938,7 @@ fn copy_directory(root: &Path, target: &Target, options: &Options) -> CopyResult
     #[cfg(any(windows, target_os = "redox"))]
     let mut hard_links: Vec<(String, u64)> = vec![];
 
-    for path in WalkDir::new(root) {
+    for path in WalkDir::new(root).same_file_system(options.one_file_system) {
         let p = or_continue!(path);
         let is_symlink = fs::symlink_metadata(p.path())?.file_type().is_symlink();
         let path = if (options.no_dereference || options.dereference) && is_symlink {
diff --git a/tests/by-util/test_cp.rs b/tests/by-util/test_cp.rs
index b96bd4e29..a00ed2fd2 100644
--- a/tests/by-util/test_cp.rs
+++ b/tests/by-util/test_cp.rs
@@ -31,6 +31,12 @@ static TEST_COPY_FROM_FOLDER: &str = "hello_dir_with_file/";
 static TEST_COPY_FROM_FOLDER_FILE: &str = "hello_dir_with_file/hello_world.txt";
 static TEST_COPY_TO_FOLDER_NEW: &str = "hello_dir_new";
 static TEST_COPY_TO_FOLDER_NEW_FILE: &str = "hello_dir_new/hello_world.txt";
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+static TEST_MOUNT_COPY_FROM_FOLDER: &str = "dir_with_mount";
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+static TEST_MOUNT_MOUNTPOINT: &str = "mount";
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+static TEST_MOUNT_OTHER_FILESYSTEM_FILE: &str = "mount/DO_NOT_copy_me.txt";
 
 #[test]
 fn test_cp_cp() {
@@ -1001,3 +1007,70 @@ fn test_cp_target_file_dev_null() {
 
     assert!(at.file_exists(file2));
 }
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+fn test_cp_one_file_system() {
+    use crate::common::util::AtPath;
+    use walkdir::WalkDir;
+
+    let scene = TestScenario::new(util_name!());
+
+    // Test must be run as root (or with `sudo -E`)
+    if scene.cmd("whoami").run().stdout != "root\n" {
+        return;
+    }
+
+    let at = scene.fixtures.clone();
+    let at_src = AtPath::new(&at.plus(TEST_MOUNT_COPY_FROM_FOLDER));
+    let at_dst = AtPath::new(&at.plus(TEST_COPY_TO_FOLDER_NEW));
+
+    // Prepare the mount
+    at_src.mkdir(TEST_MOUNT_MOUNTPOINT);
+    let mountpoint_path = &at_src.plus_as_string(TEST_MOUNT_MOUNTPOINT);
+
+    let _r = scene
+        .cmd("mount")
+        .arg("-t")
+        .arg("tmpfs")
+        .arg("-o")
+        .arg("size=640k") // ought to be enough
+        .arg("tmpfs")
+        .arg(mountpoint_path)
+        .run();
+    assert!(_r.code == Some(0), _r.stderr);
+
+    at_src.touch(TEST_MOUNT_OTHER_FILESYSTEM_FILE);
+
+    // Begin testing -x flag
+    let result = scene
+        .ucmd()
+        .arg("-rx")
+        .arg(TEST_MOUNT_COPY_FROM_FOLDER)
+        .arg(TEST_COPY_TO_FOLDER_NEW)
+        .run();
+
+    // Ditch the mount before the asserts
+    let _r = scene.cmd("umount").arg(mountpoint_path).run();
+    assert!(_r.code == Some(0), _r.stderr);
+
+    assert!(result.success);
+    assert!(!at_dst.file_exists(TEST_MOUNT_OTHER_FILESYSTEM_FILE));
+    // Check if the other files were copied from the source folder hirerarchy
+    for entry in WalkDir::new(at_src.as_string()) {
+        let entry = entry.unwrap();
+        let relative_src = entry
+            .path()
+            .strip_prefix(at_src.as_string())
+            .unwrap()
+            .to_str()
+            .unwrap();
+
+        let ft = entry.file_type();
+        match (ft.is_dir(), ft.is_file(), ft.is_symlink()) {
+            (true, _, _) => assert!(at_dst.dir_exists(relative_src)),
+            (_, true, _) => assert!(at_dst.file_exists(relative_src)),
+            (_, _, _) => panic!(),
+        }
+    }
+}
diff --git a/tests/fixtures/cp/dir_with_mount/copy_me.txt b/tests/fixtures/cp/dir_with_mount/copy_me.txt
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/fixtures/cp/dir_with_mount/copy_me/copy_me.txt b/tests/fixtures/cp/dir_with_mount/copy_me/copy_me.txt
new file mode 100644
index 000000000..e69de29bb