diff --git a/gos-concurrency-building-blocks/the-sync-package/pool/fig-sync-pool.go b/gos-concurrency-building-blocks/the-sync-package/pool/fig-sync-pool.go
index f363c71..dcb1d5e 100644
--- a/gos-concurrency-building-blocks/the-sync-package/pool/fig-sync-pool.go
+++ b/gos-concurrency-building-blocks/the-sync-package/pool/fig-sync-pool.go
@@ -7,9 +7,12 @@ import (
 
 func main() {
 	var numCalcsCreated int
+	var m sync.Mutex
 	calcPool := &sync.Pool{
 		New: func() interface{} {
+			m.Lock()
 			numCalcsCreated += 1
+			m.Unlock()
 			mem := make([]byte, 1024)
 			return &mem // <1>
 		},