diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 295d9d6..490ae86 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -48,6 +48,8 @@
 
   void* alternate_signal_stack;
 
+  pthread_mutex_t startup_handshake_mutex;
+
   /*
    * The dynamic linker implements dlerror(3), which makes it hard for us to implement this
    * per-thread buffer by simply using malloc(3) and free(3).