diff --git a/cont.c b/cont.c
index 1d88088461..b3c84d82ac 100644
--- a/cont.c
+++ b/cont.c
@@ -1201,6 +1201,8 @@ cont_save_thread(rb_context_t *cont, rb_thread_t *th)
     sec->machine.stack_end = NULL;
 }
 
+static rb_nativethread_lock_t jit_cont_lock;
+
 // Register a new continuation with execution context `ec`. Return JIT info about
 // the continuation.
 static struct rb_jit_cont *
@@ -1216,7 +1218,7 @@ jit_cont_new(rb_execution_context_t *ec)
         rb_memerror();
     cont->ec = ec;
 
-    RB_VM_LOCK_ENTER();
+    rb_native_mutex_lock(&jit_cont_lock);
     if (first_jit_cont == NULL) {
         cont->next = cont->prev = NULL;
     }
@@ -1226,7 +1228,7 @@ jit_cont_new(rb_execution_context_t *ec)
         first_jit_cont->prev = cont;
     }
     first_jit_cont = cont;
-    RB_VM_LOCK_LEAVE();
+    rb_native_mutex_unlock(&jit_cont_lock);
 
     return cont;
 }
@@ -1235,7 +1237,7 @@ jit_cont_new(rb_execution_context_t *ec)
 static void
 jit_cont_free(struct rb_jit_cont *cont)
 {
-    RB_VM_LOCK_ENTER();
+    rb_native_mutex_lock(&jit_cont_lock);
     if (cont == first_jit_cont) {
         first_jit_cont = cont->next;
         if (first_jit_cont != NULL)
@@ -1246,7 +1248,7 @@ jit_cont_free(struct rb_jit_cont *cont)
         if (cont->next != NULL)
             cont->next->prev = cont->prev;
     }
-    RB_VM_LOCK_LEAVE();
+    rb_native_mutex_unlock(&jit_cont_lock);
 
     free(cont);
 }
@@ -1273,7 +1275,7 @@ rb_jit_cont_each_iseq(rb_iseq_callback callback, void *data)
     }
 }
 
-// Finish working with continuation info.
+// Finish working with jit_cont.
 void
 rb_jit_cont_finish(void)
 {
@@ -1283,8 +1285,9 @@ rb_jit_cont_finish(void)
     struct rb_jit_cont *cont, *next;
     for (cont = first_jit_cont; cont != NULL; cont = next) {
         next = cont->next;
-        xfree(cont);
+        free(cont); // Don't use xfree because it's allocated by calloc.
     }
+    rb_native_mutex_destroy(&jit_cont_lock);
 }
 
 static void
@@ -1340,11 +1343,15 @@ rb_fiberptr_blocking(struct rb_fiber_struct *fiber)
     return fiber->blocking;
 }
 
-// This is used for root_fiber because other fibers call cont_init_mjit_cont through cont_new.
+// Start working with jit_cont.
 void
-rb_fiber_init_jit_cont(struct rb_fiber_struct *fiber)
+rb_jit_cont_init(void)
 {
-    cont_init_jit_cont(&fiber->cont);
+    if (!jit_cont_enabled)
+        return;
+
+    rb_native_mutex_initialize(&jit_cont_lock);
+    cont_init_jit_cont(&GET_EC()->fiber_ptr->cont);
 }
 
 #if 0
@@ -2273,6 +2280,7 @@ root_fiber_alloc(rb_thread_t *th)
     return fiber;
 }
 
+// Set up a "root fiber", which is the fiber that every Ractor has.
 void
 rb_threadptr_root_fiber_setup(rb_thread_t *th)
 {
@@ -2287,10 +2295,11 @@ rb_threadptr_root_fiber_setup(rb_thread_t *th)
     fiber->blocking = 1;
     fiber_status_set(fiber, FIBER_RESUMED); /* skip CREATED */
     th->ec = &fiber->cont.saved_ec;
-    // This skips jit_cont_new for the initial thread because rb_yjit_enabled_p() and
-    // mjit_enabled are false at this point. ruby_opt_init will call rb_fiber_init_jit_cont
-    // again for this root_fiber.
-    rb_fiber_init_jit_cont(fiber);
+    // When rb_threadptr_root_fiber_setup is called for the first time, mjit_enabled and
+    // rb_yjit_enabled_p() are still false. So this does nothing and rb_jit_cont_init() that is
+    // called later will take care of it. However, you still have to call cont_init_jit_cont()
+    // here for other Ractors, which are not initialized by rb_jit_cont_init().
+    cont_init_jit_cont(&fiber->cont);
 }
 
 void
diff --git a/eval.c b/eval.c
index f5c9c0f087..826ae1456e 100644
--- a/eval.c
+++ b/eval.c
@@ -253,7 +253,6 @@ rb_ec_cleanup(rb_execution_context_t *ec, int ex0)
     }
 
     mjit_finish(true); // We still need ISeqs here, so it's before rb_ec_finalize().
-    rb_jit_cont_finish();
 
     rb_ec_finalize(ec);
 
@@ -264,6 +263,8 @@ rb_ec_cleanup(rb_execution_context_t *ec, int ex0)
     th = th0;
     rb_thread_stop_timer_thread();
     ruby_vm_destruct(th->vm);
+    // For YJIT, call this after ruby_vm_destruct() frees jit_cont for the root fiber.
+    rb_jit_cont_finish();
     if (state) ruby_default_signal(state);
 
     return sysex;
diff --git a/internal/cont.h b/internal/cont.h
index 38fab4f8ac..acac0254d3 100644
--- a/internal/cont.h
+++ b/internal/cont.h
@@ -18,7 +18,7 @@ struct rb_execution_context_struct; /* in vm_core.c */
 /* cont.c */
 void rb_fiber_reset_root_local_storage(struct rb_thread_struct *);
 void ruby_register_rollback_func_for_ensure(VALUE (*ensure_func)(VALUE), VALUE (*rollback_func)(VALUE));
-void rb_fiber_init_jit_cont(struct rb_fiber_struct *fiber);
+void rb_jit_cont_init(void);
 void rb_jit_cont_each_iseq(rb_iseq_callback callback, void *data);
 void rb_jit_cont_finish(void);
 
diff --git a/ruby.c b/ruby.c
index 03aeb9b75b..037d031c52 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1613,8 +1613,13 @@ ruby_opt_init(ruby_cmdline_options_t *opt)
 
 #if USE_MJIT
     // rb_call_builtin_inits depends on RubyVM::MJIT.enabled?
-    if (opt->mjit.on)
+    if (opt->mjit.on) {
         mjit_enabled = true;
+        // rb_threadptr_root_fiber_setup for the initial thread is called before rb_yjit_enabled_p()
+        // or mjit_enabled becomes true, meaning jit_cont_new is skipped for the initial root fiber.
+        // Therefore we need to call this again here to set the initial root fiber's jit_cont.
+        rb_jit_cont_init(); // must be after mjit_enabled = true
+    }
 #endif
 
     Init_ext(); /* load statically linked extensions before rubygems */
@@ -1624,10 +1629,6 @@ ruby_opt_init(ruby_cmdline_options_t *opt)
 
     // Make sure the saved_ec of the initial thread's root_fiber is scanned by rb_jit_cont_each_ec.
     //
-    // rb_threadptr_root_fiber_setup for the initial thread is called before rb_yjit_enabled_p()
-    // or mjit_enabled becomes true, meaning jit_cont_new is skipped for the root_fiber.
-    // Therefore we need to call this again here to set the root_fiber's jit_cont.
-    rb_fiber_init_jit_cont(GET_EC()->fiber_ptr);
 #if USE_MJIT
     // mjit_init is safe only after rb_call_builtin_inits defines RubyVM::MJIT::Compiler
     if (opt->mjit.on)
@@ -1922,6 +1923,10 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
 #if USE_YJIT
     if (FEATURE_SET_P(opt->features, yjit)) {
         rb_yjit_init();
+        // rb_threadptr_root_fiber_setup for the initial thread is called before rb_yjit_enabled_p()
+        // or mjit_enabled becomes true, meaning jit_cont_new is skipped for the initial root fiber.
+        // Therefore we need to call this again here to set the initial root fiber's jit_cont.
+        rb_jit_cont_init(); // must be after rb_yjit_init(), but before parsing options raises an exception.
     }
 #endif
 #if USE_MJIT