diff --git a/pool.go b/pool.go
index 1ba2092..b957464 100644
--- a/pool.go
+++ b/pool.go
@@ -220,6 +220,9 @@ func (p *pool) SubmittedTasks() uint64 {
 }
 
 func (p *pool) WaitingTasks() uint64 {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
 	return p.tasks.Len()
 }
 
diff --git a/pool_test.go b/pool_test.go
index a185d6a..19ccecc 100644
--- a/pool_test.go
+++ b/pool_test.go
@@ -932,3 +932,29 @@ func TestTaskInvokesGoexitAndPoolRecovers(t *testing.T) {
 		t.Fatal("StopAndWait() blocked indefinitely")
 	}
 }
+
+func TestPoolWaitingTasksUnderLoad(t *testing.T) {
+	const queueSize = 64
+	pool := NewPool(4, WithQueueSize(queueSize))
+	defer pool.StopAndWait()
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		for i := 0; i < 100000; i++ {
+			pool.Go(func() {})
+		}
+	}()
+
+	for {
+		if waiting := pool.WaitingTasks(); waiting > queueSize {
+			<-done
+			t.Fatalf("waiting task count %d exceeds queue size %d", waiting, queueSize)
+		}
+		select {
+		case <-done:
+			return
+		default:
+		}
+	}
+}