diff --git a/src/main/kotlin/com/wire/github/EventsHandler.kt b/src/main/kotlin/com/wire/github/EventsHandler.kt
index 8f19a9e..5d97eea 100644
--- a/src/main/kotlin/com/wire/github/EventsHandler.kt
+++ b/src/main/kotlin/com/wire/github/EventsHandler.kt
@@ -76,8 +76,8 @@ class EventsHandler : WireEventsHandlerSuspending() {
     private fun registerRepositories(
         repositories: Set<GitHubRepository>,
         conversationId: QualifiedId
-    ): String {
-        val results = repositories.map { repository ->
+    ): String? {
+        val results = repositories.mapNotNull { repository ->
             runCatching {
                 gitHubWebhookManager.ensureWebhookForConversation(
                     repository = repository,
@@ -101,7 +101,7 @@ class EventsHandler : WireEventsHandlerSuspending() {
             )
         }
 
-        return results.joinToString(separator = "\n")
+        return results.takeIf { it.isNotEmpty() }?.joinToString("\n")
     }
 
     private fun sendMessage(
diff --git a/src/main/kotlin/com/wire/github/github/GitHubWebhookManager.kt b/src/main/kotlin/com/wire/github/github/GitHubWebhookManager.kt
index ac796be..69834bb 100644
--- a/src/main/kotlin/com/wire/github/github/GitHubWebhookManager.kt
+++ b/src/main/kotlin/com/wire/github/github/GitHubWebhookManager.kt
@@ -49,7 +49,7 @@ class GitHubWebhookManager(
             storage.sadd(
                 conversationsKey(repository.fullName),
                 conversationId.toStorageKey()
-            ) > 0
+            ) == 1L
 
         markRepositoryActive(repository.fullName)