diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
index 94b7a6806..b483c166d 100644
--- a/libc/include/sys/ucontext.h
+++ b/libc/include/sys/ucontext.h
@@ -86,6 +86,7 @@ typedef struct ucontext {
   struct ucontext *uc_link;
   stack_t uc_stack;
   sigset_t uc_sigmask;
+  char __unused[128 - sizeof(sigset_t)];
   mcontext_t uc_mcontext;
 } ucontext_t;