diff --git a/libc/include/sys/linux-syscalls.h b/libc/include/sys/linux-syscalls.h
index c4e6e45..30c58fd 100644
--- a/libc/include/sys/linux-syscalls.h
+++ b/libc/include/sys/linux-syscalls.h
@@ -42,6 +42,7 @@
 #define __NR_prctl                        (__NR_SYSCALL_BASE + 172)
 #define __NR_capget                       (__NR_SYSCALL_BASE + 184)
 #define __NR_capset                       (__NR_SYSCALL_BASE + 185)
+#define __NR_sigaltstack                  (__NR_SYSCALL_BASE + 186)
 #define __NR_acct                         (__NR_SYSCALL_BASE + 51)
 #define __NR_read                         (__NR_SYSCALL_BASE + 3)
 #define __NR_write                        (__NR_SYSCALL_BASE + 4)
diff --git a/libc/include/sys/linux-unistd.h b/libc/include/sys/linux-unistd.h
index f48dbcd..d6f706b 100644
--- a/libc/include/sys/linux-unistd.h
+++ b/libc/include/sys/linux-unistd.h
@@ -48,6 +48,7 @@
 int              prctl (int option, unsigned int arg2, unsigned int arg3, unsigned int arg4, unsigned int arg5);
 int              capget (cap_user_header_t header, cap_user_data_t data);
 int              capset (cap_user_header_t header, const cap_user_data_t data);
+int              sigaltstack (const stack_t*, stack_t*);
 int              acct (const char*  filepath);
 ssize_t          read (int, void*, size_t);
 ssize_t          write (int, const void*, size_t);