diff --git a/feed_test.go b/feed_test.go
index 641b67a..ffa44f6 100644
--- a/feed_test.go
+++ b/feed_test.go
@@ -13,7 +13,7 @@ func TestFeed_Topics(t *testing.T) {
 	subscriberReady := make(chan struct{}, 1)
 	defer close(subscriberReady)
 
-	onSubscribe := WithOnSubscribe(func(count int) {
+	onSubscribe := WithOnSubscribe(func() {
 		subscriberReady <- struct{}{}
 	})
 
diff --git a/options.go b/options.go
index eb8201e..06e7b04 100644
--- a/options.go
+++ b/options.go
@@ -1,23 +1,29 @@
 package gubgub
 
+import (
+	"sync"
+)
+
 // TopicOptions holds common options for topics.
 type TopicOptions struct {
-	// onClose is called after the Topic is closed and all messages have been delivered.
+	// onClose is called after the Topic is closed and all messages have been delivered. Even
+	// though you might call Close multiple times, topics are effectively closed only once thus
+	// this should be called only once.
 	onClose func()
 
 	// onSubscribe is called after a new subscriber is regitered.
-	onSubscribe func(count int)
+	onSubscribe func()
 }
 
 type TopicOption func(*TopicOptions)
 
 func WithOnClose(fn func()) TopicOption {
 	return func(opts *TopicOptions) {
-		opts.onClose = fn
+		opts.onClose = sync.OnceFunc(fn)
 	}
 }
 
-func WithOnSubscribe(fn func(count int)) TopicOption {
+func WithOnSubscribe(fn func()) TopicOption {
 	return func(opts *TopicOptions) {
 		opts.onSubscribe = fn
 	}
diff --git a/options_test.go b/options_test.go
new file mode 100644
index 0000000..3ff3f72
--- /dev/null
+++ b/options_test.go
@@ -0,0 +1,95 @@
+package gubgub
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWithOnClose(t *testing.T) {
+	type closable interface {
+		Close()
+	}
+
+	feedback := make(chan struct{}, 1)
+	defer close(feedback)
+	onClose := WithOnClose(func() { feedback <- struct{}{} })
+
+	testCases := []struct {
+		name  string
+		topic closable
+	}{
+		{
+			name:  "sync topic",
+			topic: NewSyncTopic[int](onClose),
+		},
+		{
+			name:  "async topic",
+			topic: NewAsyncTopic[int](onClose),
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			go tc.topic.Close()
+
+			select {
+			case <-feedback:
+				break
+
+			case <-testTimer(t, time.Second).C:
+				t.Fatalf("expected feedback by now")
+			}
+		})
+	}
+}
+
+func TestWithOnSubscribe(t *testing.T) {
+	const totalSub = 10
+
+	feedback := make(chan int, totalSub)
+	defer close(feedback)
+
+	var counter int
+	onSubscribe := WithOnSubscribe(func() {
+		counter++
+		feedback <- counter
+	})
+
+	testCases := []struct {
+		name  string
+		topic Subscribable[int]
+	}{
+		{
+			name:  "sync topic",
+			topic: NewSyncTopic[int](onSubscribe),
+		},
+		{
+			name:  "async topic",
+			topic: NewAsyncTopic[int](onSubscribe),
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			counter = 0
+
+			for range totalSub {
+				tc.topic.Subscribe(func(i int) bool { return true })
+			}
+
+			count := 0
+			timeout := testTimer(t, time.Second)
+
+			for count < totalSub {
+				select {
+				case c := <-feedback:
+					count++
+					assert.Equal(t, count, c, "expected %d but got %d instead", count, c)
+
+				case <-timeout.C:
+					t.Fatalf("expected %d feedback items by now but only got %d", totalSub, count)
+				}
+			}
+		})
+	}
+}