diff --git a/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs b/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
index 26d8a9829d5..bada158d665 100644
--- a/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
+++ b/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
@@ -4,11 +4,22 @@
 // file that was distributed with this source code.
 // spell-checker:ignore (ToDO) getreent reent IOFBF IOLBF IONBF setvbuf stderrp stdinp stdoutp
 
+#![feature(stdout_switchable_buffering)]
+
 use ctor::ctor;
 use libc::{_IOFBF, _IOLBF, _IONBF, FILE, c_char, c_int, fileno, size_t};
 use std::env;
+use std::io::{self, BufferMode};
 use std::ptr;
 
+fn value_to_buffer_mode(value: &str) -> BufferMode {
+    match value {
+        "0" => BufferMode::Immediate,
+        "L" => BufferMode::Line,
+        _ => BufferMode::Block,
+    }
+}
+
 // This runs automatically when the library is loaded via LD_PRELOAD
 #[ctor]
 fn init() {
@@ -224,6 +235,9 @@ pub unsafe extern "C" fn __stdbuf() {
         set_buffer(unsafe { __stdbuf_get_stdin() }, &val);
     }
     if let Ok(val) = env::var("_STDBUF_O") {
+        io::stdout()
+            .lock()
+            .set_buffer_mode(value_to_buffer_mode(&val));
         set_buffer(unsafe { __stdbuf_get_stdout() }, &val);
     }
 }
diff --git a/src/uu/uniq/src/uniq.rs b/src/uu/uniq/src/uniq.rs
index 109e49d6224..5172dd40fe5 100644
--- a/src/uu/uniq/src/uniq.rs
+++ b/src/uu/uniq/src/uniq.rs
@@ -843,9 +843,6 @@ fn open_output_file(out_file_name: Option<&OsStr>) -> UResult<Box<dyn Write>> {
             )?;
             Box::new(BufWriter::with_capacity(OUTPUT_BUFFER_CAPACITY, out_file))
         }
-        _ => Box::new(BufWriter::with_capacity(
-            OUTPUT_BUFFER_CAPACITY,
-            stdout().lock(),
-        )),
+        _ => Box::new(stdout().lock()),
     })
 }
diff --git a/test-stdbuf-poc.sh b/test-stdbuf-poc.sh
new file mode 100755
index 00000000000..6be5ea56458
--- /dev/null
+++ b/test-stdbuf-poc.sh
@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# requires stage1 rustc built from https://github.com/victor-prokhorov/rust/commit/a9d5767288d132bc3688799ad45c4647b7043f7d
+# which is a clone of https://github.com/rust-lang/rust/pull/78515
+set -euo pipefail
+
+COREUTILS_DIR=/home/victorprokhorov/coreutils
+RUST_DIR=/home/victorprokhorov/rust-lang/rust
+GNU_DIR=/home/victorprokhorov/gnu
+STAGE1_SYSROOT_LIB="$RUST_DIR/build/aarch64-unknown-linux-gnu/stage1/lib/rustlib/aarch64-unknown-linux-gnu/lib"
+STAGE1_RUSTC="$RUST_DIR/build/aarch64-unknown-linux-gnu/stage1/bin/rustc"
+
+ok()   { echo "  OK  $*"; }
+fail() { echo "FAIL $*"; exit 1; }
+step() { echo; echo "$*"; }
+
+step "build stdlib"
+cd "$RUST_DIR"
+python3 x.py build library
+ok "stdlib built"
+
+step "toolchain check"
+rustup run stage1 rustc --version | grep -q 'rustc' \
+  || fail "stage1 toolchain not found"
+ok "$(rustup run stage1 rustc --version)"
+rustup run stage1 rustc --edition 2021 -C prefer-dynamic \
+  -o /tmp/poc_api_check - <<'RUST' \
+  || fail "stdout_switchable_buffering or set_buffer_mode not found in stage1 stdlib"
+#![feature(stdout_switchable_buffering)]
+use std::io::{self, BufferMode};
+fn main() { io::stdout().lock().set_buffer_mode(BufferMode::Line); }
+RUST
+ok "stage1 stdlib has stdout_switchable_buffering and set_buffer_mode"
+
+step "cargo +stage1 build"
+cd "$COREUTILS_DIR"
+RUSTC="$STAGE1_RUSTC" cargo build -p uu_stdbuf_libstdbuf -p uu_stdbuf -p uu_uniq
+
+step "block buffering test all lines must appear together at the end"
+rustup run stage1 rustc --edition 2021 -C prefer-dynamic \
+  -o /tmp/poc_block_test - <<'RUST' || fail "compile poc_block_test"
+#![feature(stdout_switchable_buffering)]
+use std::io::{self, BufferMode};
+fn main() {
+    io::stdout().lock().set_buffer_mode(BufferMode::Block);
+    for line in ["1", "2", "3", "soleil"] {
+        println!("{line}");
+        std::thread::sleep(std::time::Duration::from_secs(1));
+    }
+}
+RUST
+LD_LIBRARY_PATH="$STAGE1_SYSROOT_LIB" /tmp/poc_block_test
+
+step "GNU compliance tests/misc/stdbuf.sh"
+cd "$COREUTILS_DIR"
+path_UUTILS="$COREUTILS_DIR" path_GNU="$GNU_DIR" PROFILE=debug \
+  util/run-gnu-test.sh tests/misc/stdbuf.sh