diff --git a/sync.go b/sync.go
index 6dd426d..1959bb0 100644
--- a/sync.go
+++ b/sync.go
@@ -17,11 +17,11 @@ type SyncTopic[T any] struct {
 	subscribers []Subscriber[T]
 }
 
-// NewSyncTopic creates a zero SyncTopic and return a pointer to it.
+// NewSyncTopic creates a SyncTopic with the specified options.
 func NewSyncTopic[T any](opts ...TopicOption) *SyncTopic[T] {
 	options := TopicOptions{
 		onClose:     func() {},
-		onSubscribe: func(count int) {},
+		onSubscribe: func() {},
 	}
 
 	for _, opt := range opts {
@@ -33,7 +33,7 @@ func NewSyncTopic[T any](opts ...TopicOption) *SyncTopic[T] {
 	}
 }
 
-// Close will cause future Publish and Subscribe calls to return an error.
+// Close will prevent further publishing and subscribing.
 func (t *SyncTopic[T]) Close() {
 	t.closed.Store(true)
 	t.options.onClose()
@@ -63,7 +63,7 @@ func (t *SyncTopic[T]) Subscribe(fn Subscriber[T]) error {
 	defer t.mu.Unlock()
 
 	t.subscribers = append(t.subscribers, fn)
-	t.options.onSubscribe(len(t.subscribers))
+	t.options.onSubscribe()
 
 	return nil
 }
diff --git a/sync_test.go b/sync_test.go
index 368970e..ea8ab14 100644
--- a/sync_test.go
+++ b/sync_test.go
@@ -69,3 +69,35 @@ func TestSyncTopic_MultiPublishersMultiSubscribers(t *testing.T) {
 
 	assert.Equal(t, msgCount*subCount, feedbackCounter)
 }
+
+func TestSyncTopic_ClosedTopicError(t *testing.T) {
+	testCases := []struct {
+		name     string
+		assertFn func(*SyncTopic[int])
+	}{
+		{
+			name: "publishing returns error",
+			assertFn: func(topic *SyncTopic[int]) {
+				assert.Error(t, ErrTopicClosed, topic.Publish(1))
+			},
+		},
+		{
+			name: "subscribing returns error",
+			assertFn: func(topic *SyncTopic[int]) {
+				assert.Error(t, ErrTopicClosed, topic.Subscribe(func(i int) bool { return true }))
+			},
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			feedback := make(chan struct{}, 1)
+			defer close(feedback)
+
+			topic := NewSyncTopic[int]()
+
+			topic.Close() // this should close the topic, no more messages can be published
+
+			tc.assertFn(topic)
+		})
+	}
+}