diff --git a/cache_test.go b/cache_test.go
index 2972707..671161e 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -246,7 +246,7 @@ func TestCache_EstimatedSize(t *testing.T) {
 	})
 	wg.Go(func() error {
 		defer cfn()
-		for i := 0; i < 1000000; i++ {
+		for i := 0; i < 1200; i++ {
 			if i%2 == 0 {
 				client.Set(i, 1, 1)
 			} else {
@@ -256,6 +256,8 @@ func TestCache_EstimatedSize(t *testing.T) {
 		return nil
 	})
 	require.Nil(t, wg.Wait())
+	client.Wait()
+	require.Equal(t, 500, client.EstimatedSize())
 }
 
 func TestCache_Doorkeeper(t *testing.T) {
diff --git a/internal/store.go b/internal/store.go
index d12b9ef..139eda4 100644
--- a/internal/store.go
+++ b/internal/store.go
@@ -463,7 +463,7 @@ func (s *Store[K, V]) Len() int {
 
 func (s *Store[K, V]) EstimatedSize() int {
 	s.policyMu.Lock()
-	total := s.policy.slru.protected.Len() + s.policy.slru.probation.Len()
+	total := s.policy.window.Len() + s.policy.slru.protected.Len() + s.policy.slru.probation.Len()
 	s.policyMu.Unlock()
 	return total
 }