diff --git a/outbox/delete.go b/outbox/delete.go
index 6d32a4da..3a7c67f4 100644
--- a/outbox/delete.go
+++ b/outbox/delete.go
@@ -99,7 +99,7 @@ func Delete(ctx context.Context, domain string, cfg *cfg.Config, db *sql.DB, not
 
 	if _, err := tx.ExecContext(
 		ctx,
-		`INSERT INTO outbox (activity, sender) VALUES (?,?)`,
+		`INSERT OR IGNORE INTO outbox (activity, sender) VALUES (?,?)`,
 		string(j),
 		note.AttributedTo,
 	); err != nil {
diff --git a/test/delete_test.go b/test/delete_test.go
index e8d7ab27..6f8a9445 100644
--- a/test/delete_test.go
+++ b/test/delete_test.go
@@ -95,3 +95,61 @@ func TestDelete_UnauthenticatedUser(t *testing.T) {
 	view = server.Handle("/users/view/"+id, server.Alice)
 	assert.Contains(view, "Hello world")
 }
+
+func TestDelete_WithReply(t *testing.T) {
+	server := newTestServer()
+	defer server.Shutdown()
+
+	assert := assert.New(t)
+
+	say := server.Handle("/users/say?Hello%20world", server.Alice)
+	assert.Regexp(`30 /users/view/\S+\r\n$`, say)
+
+	postID := say[15 : len(say)-2]
+
+	reply := server.Handle(fmt.Sprintf("/users/reply/%s?Welcome%%20Alice", postID), server.Bob)
+	assert.Regexp(`^30 /users/view/\S+\r\n$`, reply)
+
+	replyID := reply[15 : len(reply)-2]
+
+	delete := server.Handle("/users/delete/"+replyID, server.Bob)
+	assert.Equal(fmt.Sprintf("30 /users/outbox/%s\r\n", strings.TrimPrefix(server.Bob.ID, "https://")), delete)
+
+	view := server.Handle("/users/view/"+replyID, server.Alice)
+	assert.Equal(view, "40 Post not found\r\n")
+
+	delete = server.Handle("/users/delete/"+postID, server.Alice)
+	assert.Equal(fmt.Sprintf("30 /users/outbox/%s\r\n", strings.TrimPrefix(server.Alice.ID, "https://")), delete)
+
+	view = server.Handle("/users/view/"+postID, server.Alice)
+	assert.Equal(view, "40 Post not found\r\n")
+}
+
+func TestDelete_WithReplyPostDeletedFirst(t *testing.T) {
+	server := newTestServer()
+	defer server.Shutdown()
+
+	assert := assert.New(t)
+
+	say := server.Handle("/users/say?Hello%20world", server.Alice)
+	assert.Regexp(`30 /users/view/\S+\r\n$`, say)
+
+	postID := say[15 : len(say)-2]
+
+	reply := server.Handle(fmt.Sprintf("/users/reply/%s?Welcome%%20Alice", postID), server.Bob)
+	assert.Regexp(`^30 /users/view/\S+\r\n$`, reply)
+
+	replyID := reply[15 : len(reply)-2]
+
+	delete := server.Handle("/users/delete/"+postID, server.Alice)
+	assert.Equal(fmt.Sprintf("30 /users/outbox/%s\r\n", strings.TrimPrefix(server.Alice.ID, "https://")), delete)
+
+	view := server.Handle("/users/view/"+postID, server.Alice)
+	assert.Equal(view, "40 Post not found\r\n")
+
+	delete = server.Handle("/users/delete/"+replyID, server.Bob)
+	assert.Equal(fmt.Sprintf("30 /users/outbox/%s\r\n", strings.TrimPrefix(server.Bob.ID, "https://")), delete)
+
+	view = server.Handle("/users/view/"+replyID, server.Alice)
+	assert.Equal(view, "40 Post not found\r\n")
+}