diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 48b2bca..21d34fb 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -108,6 +108,14 @@
 
 #define PTHREAD_BARRIER_SERIAL_THREAD -1
 
+typedef struct {
+#if defined(__LP64__)
+  int64_t __private;
+#else
+  int32_t __private[2];
+#endif
+} pthread_spinlock_t;
+
 #if defined(__LP64__)
 #define PTHREAD_STACK_MIN (4 * PAGE_SIZE)
 #else
@@ -229,6 +237,12 @@
 int pthread_barrier_destroy(pthread_barrier_t*) __nonnull((1));
 int pthread_barrier_wait(pthread_barrier_t*) __nonnull((1));
 
+int pthread_spin_destroy(pthread_spinlock_t*) __nonnull((1));
+int pthread_spin_init(pthread_spinlock_t*, int) __nonnull((1));
+int pthread_spin_lock(pthread_spinlock_t*) __nonnull((1));
+int pthread_spin_trylock(pthread_spinlock_t*) __nonnull((1));
+int pthread_spin_unlock(pthread_spinlock_t*) __nonnull((1));
+
 pthread_t pthread_self(void) __pure2;
 
 int pthread_setname_np(pthread_t, const char*) __nonnull((2));