1 files changed, 5 insertions, 1 deletions
diff --git a/thread.c b/thread.c
index ead451ccdd..c5bf767bcb 100644
--- a/thread.c
+++ b/thread.c
@@ -374,6 +374,10 @@ thread_create_core(VALUE thval, VALUE args, VALUE (*fn)(ANYARGS))
 {
     rb_thread_t *th;
 
+    if (OBJ_FROZEN(GET_THREAD()->thgroup)) {
+	rb_raise(rb_eThreadError,
+		 "can't start a new thread (frozen ThreadGroup)");
+    }
     GetThreadPtr(thval, th);
 
     /* setup thread environment */
@@ -382,7 +386,7 @@ thread_create_core(VALUE thval, VALUE args, VALUE (*fn)(ANYARGS))
     th->first_func = fn;
 
     th->priority = GET_THREAD()->priority;
-    th->thgroup = th->vm->thgroup_default;
+    th->thgroup = GET_THREAD()->thgroup;
 
     native_mutex_initialize(&th->interrupt_lock);
     /* kick thread */