--- sigreturn.c
+++ sigreturn.c
@@ -12,6 +12,8 @@
 #elif NSIG < 32
 # error NSIG < 32
 #endif
+extern uint64_t *const aarch64_sp_ptr;
+extern uint32_t *const arm_sp_ptr;
 
 int
 sys_sigreturn(struct tcb *tcp)