diff --git a/thread.c b/thread.c
index e429808fc9..56fd7f9926 100644
--- a/thread.c
+++ b/thread.c
@@ -73,6 +73,7 @@
 #include "ruby/debug.h"
 #include "internal.h"
 #include "iseq.h"
+#include "vm_core.h"
 
 #ifndef USE_NATIVE_THREAD_PRIORITY
 #define USE_NATIVE_THREAD_PRIORITY 0
@@ -2243,10 +2244,6 @@ rb_threadptr_signal_exit(rb_thread_t *th)
     rb_threadptr_raise(th->vm->main_thread, 2, argv);
 }
 
-#if defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK)
-#define USE_SIGALTSTACK
-#endif
-
 int
 rb_ec_set_raised(rb_execution_context_t *ec)
 {