diff --git a/ext/mini_racer_extension/mini_racer_extension.c b/ext/mini_racer_extension/mini_racer_extension.c
index 496d011..e3adfb8 100644
--- a/ext/mini_racer_extension/mini_racer_extension.c
+++ b/ext/mini_racer_extension/mini_racer_extension.c
@@ -1603,6 +1603,21 @@ void v8_get_flags(char **p, size_t *n)
         rb_thread_lock_native_thread();
 }
 
+// Blocks until the V8 thread finishes booting the isolate, which includes
+// snapshot deserialization (v8::Isolate::New) and safe-context setup. None of
+// that touches Ruby objects -- the snapshot is a plain C buffer already copied
+// into |c->snapshot| -- so we release the GVL while waiting, letting other Ruby
+// threads (e.g. a background pool refilling more contexts) truly run meanwhile.
+static void *context_boot_wait(void *arg)
+{
+    Context *c;
+
+    c = arg;
+    barrier_wait(&c->early_init);
+    barrier_wait(&c->late_init);
+    return NULL;
+}
+
 static VALUE context_initialize(int argc, VALUE *argv, VALUE self)
 {
     VALUE kwargs, a, k, v;
@@ -1670,8 +1685,7 @@ static VALUE context_initialize(int argc, VALUE *argv, VALUE self)
         pthread_attr_destroy(&attr);
         if (r)
             goto fail;
-        barrier_wait(&c->early_init);
-        barrier_wait(&c->late_init);
+        rb_thread_call_without_gvl(context_boot_wait, c, NULL, NULL);
     }
     return Qnil;
 fail: