1 files changed, 1 insertions, 0 deletions
diff --git a/cont.c b/cont.c
index 095cc86767..a43950c6cb 100644
--- a/cont.c
+++ b/cont.c
@@ -1288,6 +1288,7 @@ root_fiber_alloc(rb_thread_t *th)
     rb_fiber_t *fib;
     /* no need to allocate vm stack */
     fib = fiber_t_alloc(fiber_alloc(rb_cFiber));
+    fib->cont.saved_thread.ec.stack = NULL;
     fib->cont.type = ROOT_FIBER_CONTEXT;
 #if FIBER_USE_NATIVE
 #ifdef _WIN32