diff --git a/Cargo.toml b/Cargo.toml
index 3fb998d..18434e0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,3 +7,4 @@ edition = "2021"
 
 [dependencies]
 libc = "0.2.116"
+once_cell = "1.0"
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 2363e0e..137a85f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,7 @@
 #![feature(thread_local)]
+#![feature(const_btree_new)]
 #![allow(non_camel_case_types)]
+#![allow(clippy::missing_safety_doc)]
 
 /// Call this somewhere to force Rust to link this module.
 /// The call doesn't need to execute, just exist.
@@ -37,11 +39,7 @@ extern "C" {
 
     fn CondVar_Init(cv: *mut CondVar);
     fn CondVar_Wait(cv: *mut CondVar, lock: *mut LightLock);
-    fn CondVar_WaitTimeout(
-        cv: *mut CondVar,
-        lock: *mut LightLock,
-        timeout_ns: i64,
-    ) -> libc::c_int;
+    fn CondVar_WaitTimeout(cv: *mut CondVar, lock: *mut LightLock, timeout_ns: i64) -> libc::c_int;
     fn CondVar_WakeUp(cv: *mut CondVar, num_threads: i32);
 }
 
@@ -246,9 +244,7 @@ fn init_rwlock(lock: *mut libc::pthread_rwlock_t) {
     let lock = lock as *mut rwlock_clear;
 
     unsafe {
-        if (*lock).initialized {
-            return
-        } else {
+        if !(*lock).initialized {
             let mut attr = std::mem::MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
             pthread_mutexattr_init(attr.as_mut_ptr());
             let mut attr = attr.assume_init();
@@ -306,7 +302,7 @@ pub unsafe extern "C" fn pthread_rwlock_tryrdlock(
     let lock = lock as *mut rwlock_clear;
 
     if pthread_mutex_trylock(&mut (*lock).mutex) != 0 {
-        return -1
+        return -1;
     }
 
     while (*lock).writer_active {
@@ -346,7 +342,7 @@ pub unsafe extern "C" fn pthread_rwlock_trywrlock(
     let lock = lock as *mut rwlock_clear;
 
     if pthread_mutex_trylock(&mut (*lock).mutex) != 0 {
-        return -1
+        return -1;
     }
 
     while (*lock).writer_active || (*lock).num_readers > 0 {
@@ -403,67 +399,66 @@ pub unsafe extern "C" fn pthread_rwlockattr_destroy(
 
 // THREAD KEYS IMPLEMENTATION FOR RUST STD
 
+use once_cell::sync::Lazy;
 use std::collections::BTreeMap;
 use std::ptr;
 use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{PoisonError, RwLock};
 
-pub type Key = usize;
-
-type Dtor = unsafe extern "C" fn(*mut u8);
+type Key = usize;
+type Destructor = unsafe extern "C" fn(*mut libc::c_void);
 
 static NEXT_KEY: AtomicUsize = AtomicUsize::new(1);
 
-static mut KEYS: *mut BTreeMap<Key, Option<Dtor>> = ptr::null_mut();
+static KEYS: Lazy<RwLock<BTreeMap<Key, Option<Destructor>>>> = Lazy::new(RwLock::default);
 
 #[thread_local]
-static mut LOCALS: *mut BTreeMap<Key, *mut u8> = ptr::null_mut();
-
-unsafe fn keys() -> &'static mut BTreeMap<Key, Option<Dtor>> {
-    if KEYS == ptr::null_mut() {
-        KEYS = Box::into_raw(Box::new(BTreeMap::new()));
-    }
-    &mut *KEYS
-}
-
-unsafe fn locals() -> &'static mut BTreeMap<Key, *mut u8> {
-    if LOCALS == ptr::null_mut() {
-        LOCALS = Box::into_raw(Box::new(BTreeMap::new()));
-    }
-    &mut *LOCALS
-}
+static mut LOCALS: BTreeMap<Key, *mut libc::c_void> = BTreeMap::new();
 
-#[inline]
-pub unsafe fn create(dtor: Option<unsafe extern "C" fn(*mut u8)>) -> Key {
-    let key = NEXT_KEY.fetch_add(1, Ordering::SeqCst);
-    keys().insert(key, dtor);
-    key
+fn is_valid_key(key: Key) -> bool {
+    KEYS.read()
+        .unwrap_or_else(PoisonError::into_inner)
+        .contains_key(&(key as Key))
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn pthread_key_create(
     key: *mut libc::pthread_key_t,
-    dtor: Option<unsafe extern "C" fn(*mut libc::c_void)>,
+    destructor: Option<Destructor>,
 ) -> libc::c_int {
     let new_key = NEXT_KEY.fetch_add(1, Ordering::SeqCst);
-    keys().insert(new_key, std::mem::transmute(dtor));
+    KEYS.write()
+        .unwrap_or_else(PoisonError::into_inner)
+        .insert(new_key, destructor);
 
-    *key = new_key as u32;
+    *key = new_key as libc::pthread_key_t;
 
     0
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn pthread_key_delete(key: libc::pthread_key_t) -> libc::c_int {
-    keys().remove(&(key as usize));
-
-    0
+    match KEYS
+        .write()
+        .unwrap_or_else(PoisonError::into_inner)
+        .remove(&(key as Key))
+    {
+        // We had a entry, so it was a valid key.
+        // It's officially undefined behavior if they use the key after this,
+        // so don't worry about cleaning up LOCALS, especially since we can't
+        // clean up every thread's map.
+        Some(_) => 0,
+        // The key is unknown
+        None => libc::EINVAL,
+    }
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn pthread_getspecific(key: libc::pthread_key_t) -> *mut libc::c_void {
-    if let Some(&entry) = locals().get(&(key as usize)) {
-        entry as _
+    if let Some(&value) = LOCALS.get(&(key as Key)) {
+        value as _
     } else {
+        // Note: we don't care if the key is invalid, we still return null
         ptr::null_mut()
     }
 }
@@ -473,6 +468,12 @@ pub unsafe extern "C" fn pthread_setspecific(
     key: libc::pthread_key_t,
     value: *const libc::c_void,
 ) -> libc::c_int {
-    locals().insert(key as usize, std::mem::transmute(value));
+    let key = key as Key;
+
+    if !is_valid_key(key) {
+        return libc::EINVAL;
+    }
+
+    LOCALS.insert(key, value as *mut _);
     0
 }