diff --git a/agents/src/span_collector.cc b/agents/src/span_collector.cc
index 3e429c65f8..8aafe53dee 100644
--- a/agents/src/span_collector.cc
+++ b/agents/src/span_collector.cc
@@ -34,7 +34,12 @@ void SpanCollector::do_collect() {
       // Only notify the loop_ thread if the queue reaches min_span_count_to
       // avoid too many uv_async_t::send() calls.
       if (collector->span_msg_q_.enqueue(span) > collector->min_span_count_) {
-        ASSERT_EQ(0, collector->span_msg_->send());
+        if (!collector->sent_) {
+          ASSERT_EQ(0, collector->span_msg_->send());
+          collector->sent_ = true;
+        }
+      } else if (collector->sent_) {
+        collector->sent_ = false;
       }
     },
     weak_from_this());
diff --git a/agents/src/span_collector.h b/agents/src/span_collector.h
index 71e23197bd..3e666889db 100644
--- a/agents/src/span_collector.h
+++ b/agents/src/span_collector.h
@@ -83,6 +83,7 @@ class SpanCollector: public std::enable_shared_from_this<SpanCollector> {
   nsuv::ns_timer* span_timer_;
   std::function<void(const SpanVector&)> callback_ = nullptr;
   std::function<void(const SpanVector&)> transform_callback_ = nullptr;
+  bool sent_ = false;
 };
 
 }  // namespace nsolid