diff --git a/library/std/src/os/mikros/mod.rs b/library/std/src/os/mikros/mod.rs
index 07f8179b5e7..fad0564f867 100644
--- a/library/std/src/os/mikros/mod.rs
+++ b/library/std/src/os/mikros/mod.rs
@@ -11,6 +11,8 @@
 
 mod errno;
 
+use serde::{Serialize, Serializer, ser::SerializeTupleVariant};
+
 #[stable(feature = "mikros", since = "1.80.0")]
 pub use errno::Errno;
 
@@ -74,3 +76,59 @@ pub mod prelude {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub use super::ffi::{OsStrExt, OsStringExt};
 }
+
+#[unstable(feature = "rmp", issue = "none")]
+impl Serialize for FileCreationMode {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            Self::NoCreate => serializer.serialize_unit_variant("FileCreationMode", 0, "NoCreate"),
+            Self::Create => serializer.serialize_unit_variant("FileCreationMode", 1, "Create"),
+            Self::ForceCreate => serializer.serialize_unit_variant("FileCreationMode", 2, "ForceCreate"),
+        }
+    }
+}
+
+#[unstable(feature = "rmp", issue = "none")]
+impl Serialize for FileWriteMode {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            Self::Start => serializer.serialize_unit_variant("FileWriteMode", 0, "Start"),
+            Self::Truncate => serializer.serialize_unit_variant("FileWriteMode", 1, "Truncate"),
+            Self::Append => serializer.serialize_unit_variant("FileWriteMode", 2, "Append"),
+        }
+    }
+}
+
+#[unstable(feature = "rmp", issue = "none")]
+impl Serialize for FileOpenMode {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            Self::Read => serializer.serialize_unit_variant("FileOpenMode", 0, "Read"),
+            Self::Write(ref wr_mode, ref cr_mode) => {
+                let mut tv = serializer.serialize_tuple_variant("FileOpenMode", 1, "Write", 2)?;
+                tv.serialize_field(wr_mode)?;
+                tv.serialize_field(cr_mode)?;
+                tv.end()
+            },
+            Self::ReadWrite(ref wr_mode, ref cr_mode) => {
+                let mut tv = serializer.serialize_tuple_variant("FileOpenMode", 2, "ReadWrite", 2)?;
+                tv.serialize_field(wr_mode)?;
+                tv.serialize_field(cr_mode)?;
+                tv.end()
+            },
+
+        }
+    }
+}
diff --git a/library/std/src/sys/pal/mikros/fs.rs b/library/std/src/sys/pal/mikros/fs.rs
index 28cbf02d51a..58081f3a276 100644
--- a/library/std/src/sys/pal/mikros/fs.rs
+++ b/library/std/src/sys/pal/mikros/fs.rs
@@ -389,7 +389,8 @@ fn get_open_mode(&self) -> io::Result<FileOpenMode> {
 
 
 impl File {
-    pub fn open(path: &Path, _opts: &OpenOptions) -> io::Result<File> {
+    pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
+        let open_mode = opts.get_open_mode()?;
         let path = path.canonicalize()?;
         let vfs_pid = loop {
             if let Some(pid) = syscalls::try_get_registered(0) {
@@ -397,7 +398,7 @@ pub fn open(path: &Path, _opts: &OpenOptions) -> io::Result<File> {
             }
         };
         let open_res: Result<(u64, u64), Errno> = postcard::from_bytes(
-            &rpc::send_call(vfs_pid, 2, 2, &postcard::to_allocvec(&path).unwrap()).get_return(),
+            &rpc::send_call(vfs_pid, 2, 2, &postcard::to_allocvec(&(path, open_mode)).unwrap()).get_return(),
         )
         .unwrap();
         let (fs_pid, fd) = open_res?;