diff --git a/pool.go b/pool.go
index 7a7a48e..987ba4d 100644
--- a/pool.go
+++ b/pool.go
@@ -77,7 +77,7 @@ func (p *Pool) periodicallyPurge() {
 			idleWorkers[i] = nil
 		}
 		if n > -1 {
-			if n >= len(idleWorkers) {
+			if n >= len(idleWorkers)-1 {
 				p.workers = idleWorkers[:0]
 			} else {
 				p.workers = idleWorkers[n+1:]
diff --git a/pool_func.go b/pool_func.go
index 7c0df59..6051117 100644
--- a/pool_func.go
+++ b/pool_func.go
@@ -78,7 +78,7 @@ func (p *PoolWithFunc) periodicallyPurge() {
 			idleWorkers[i] = nil
 		}
 		if n > -1 {
-			if n >= len(idleWorkers) {
+			if n >= len(idleWorkers)-1 {
 				p.workers = idleWorkers[:0]
 			} else {
 				p.workers = idleWorkers[n+1:]