diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index e34788b..98199d3 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -47,6 +47,8 @@
     __pthread_cleanup_t*        cleanup_stack;
     void**                      tls;         /* thread-local storage area */
 
+    void* alternate_signal_stack;
+
     /*
      * 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).