1 files changed, 1 insertions, 1 deletions
diff --git a/gc.c b/gc.c
index 4c5e2b48a8..c87526d016 100644
--- a/gc.c
+++ b/gc.c
@@ -574,7 +574,7 @@ init_heap(rb_objspace_t *objspace)
 	/* altstack of another threads are allocated in another place */
 	rb_thread_t *th = GET_THREAD();
 	void *tmp = th->altstack;
-	th->altstack = malloc(ALT_STACK_SIZE);
+	th->altstack = malloc(rb_sigaltstack_size());
 	free(tmp); /* free previously allocated area */
     }
 #endif