diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index d7289f5a95b14f..794757a8b1ed58 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -721,7 +721,7 @@ def check_coredump
 end
 
 def mmtk?
-  `#{BT.ruby} -e 'p defined?(GC::MMTk)'`.strip == '"constant"'
+  `#{BT.ruby} -e 'print (defined?(GC::MMTk.enabled?) && GC::MMTk.enabled?) || false'` == 'true'
 end
 
 exit main