diff --git a/crates/chanora_audio/src/ptt_backends/windows.rs b/crates/chanora_audio/src/ptt_backends/windows.rs
index 4b06b6d..d546f65 100644
--- a/crates/chanora_audio/src/ptt_backends/windows.rs
+++ b/crates/chanora_audio/src/ptt_backends/windows.rs
@@ -370,7 +370,7 @@ impl Drop for WindowsRawInputBackend {
 /// # Safety
 /// Calls into Win32 directly. Must be invoked on the thread that
 /// owns the message window (created here).
-unsafe fn run_raw_input_loop(init_tx: std::sync::mpsc::Sender<bool>) -> bool {
+unsafe fn run_raw_input_loop(init_tx: std::sync::mpsc::SyncSender<bool>) -> bool {
     // Helper that signals the readiness state to the main thread.
     // We send exactly once at the first decisive moment (either an
     // early-fail return or right after a successful
@@ -795,7 +795,7 @@ impl Drop for WindowsHookBackend {
 /// # Safety
 /// Calls Win32 directly; must run on the thread that owns the
 /// hook handles.
-unsafe fn run_hook_loop(init_tx: std::sync::mpsc::Sender<bool>) -> bool {
+unsafe fn run_hook_loop(init_tx: std::sync::mpsc::SyncSender<bool>) -> bool {
     let mut signal = Some(init_tx);
     macro_rules! report {
         ($v:expr) => {