diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index 78f3143cd5..dcaabc9743 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -367,7 +367,9 @@ def assert_normal_exit(testsrc, *rest, timeout: nil, **opt)
 end
 
 def assert_finish(timeout_seconds, testsrc, message = '')
-  timeout_seconds *= 3 if RubyVM::MJIT.enabled? # for --jit-wait
+  if RubyVM.const_defined? :MJIT
+    timeout_seconds *= 3 if RubyVM::MJIT.enabled? # for --jit-wait
+  end
   newtest
   show_progress(message) {
     faildesc = nil