1 files changed, 10 insertions, 2 deletions
diff --git a/thread.c b/thread.c
index a56f264a6c..a75990ccfb 100644
--- a/thread.c
+++ b/thread.c
@@ -491,8 +491,16 @@ thread_start_func_2(rb_thread_t *th, VALUE *stack_start, VALUE *register_stack_s
 	    if (state == TAG_FATAL) {
 		/* fatal error within this thread, need to stop whole script */
 	    }
-	    else if (th->vm->thread_abort_on_exception ||
-		     th->abort_on_exception || RTEST(ruby_debug)) {
+	    else if (rb_obj_is_kind_of(errinfo, rb_eSystemExit)) {
+		if (th->safe_level >= 4) {
+		    th->errinfo = rb_exc_new3(rb_eSecurityError,
+					      rb_sprintf("Insecure exit at level %d", th->safe_level));
+		    errinfo = Qnil;
+		}
+	    }
+	    else if (th->safe_level < 4 &&
+		     (th->vm->thread_abort_on_exception ||
+		      th->abort_on_exception || RTEST(ruby_debug))) {
 		/* exit on main_thread */
 	    }
 	    else {