diff --git a/pool.go b/pool.go
index c3f5568..656bf19 100644
--- a/pool.go
+++ b/pool.go
@@ -78,7 +78,7 @@ func (p *Pool) periodicallyPurge() {
 		}
 		n++
 		if n > 0 {
-			if n >= cap(idleWorkers) {
+			if n >= len(idleWorkers) {
 				p.workers = idleWorkers[:0]
 			} else {
 				p.workers = idleWorkers[n:]
diff --git a/pool_func.go b/pool_func.go
index 3e6dc5e..0b2eed5 100644
--- a/pool_func.go
+++ b/pool_func.go
@@ -79,7 +79,7 @@ func (p *PoolWithFunc) periodicallyPurge() {
 		}
 		n++
 		if n > 0 {
-			if n >= cap(idleWorkers) {
+			if n >= len(idleWorkers) {
 				p.workers = idleWorkers[:0]
 			} else {
 				p.workers = idleWorkers[n:]