diff --git a/docs/api.rst b/docs/api.rst
index 39051ae3..403b3858 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -41,5 +41,6 @@ Artifact
    optuna_dashboard.artifact.file_system.FileSystemBackend
    optuna_dashboard.artifact.boto3.Boto3Backend
    optuna_dashboard.artifact.backoff.Backoff
+   optuna_dashboard.artifact.prefix.AppendPrefix
    optuna_dashboard.artifact.protocol.ArtifactBackend
    optuna_dashboard.artifact.exceptions.ArtifactNotFound