diff --git a/ruby.c b/ruby.c
index b185b98a18..79fb6d1635 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1607,7 +1607,9 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     ruby_gc_set_params(opt->safe_level);
     ruby_init_loadpath_safe(opt->safe_level);
 
+#ifndef MJIT_FORCE_ENABLE /* to use with: ./configure cppflags="-DMJIT_FORCE_ENABLE" */
     if (opt->mjit.on)
+#endif
         /* Using TMP_RUBY_PREFIX created by ruby_init_loadpath_safe(). */
         mjit_init(&opt->mjit);