diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
index b8d4d58..dd2a0bb 100644
--- a/libc/include/sys/ucontext.h
+++ b/libc/include/sys/ucontext.h
@@ -78,6 +78,10 @@
 
 #elif defined(__aarch64__)
 
+#define NGREG 34 /* x0..x30 + sp + pc + pstate */
+typedef unsigned long greg_t;
+typedef greg_t gregset_t[NGREG];
+
 #include <asm/sigcontext.h>
 typedef struct sigcontext mcontext_t;