diff --git a/codex-rs/protocol/src/approvals.rs b/codex-rs/protocol/src/approvals.rs
index ee3572aba1..e6c51a4f81 100644
--- a/codex-rs/protocol/src/approvals.rs
+++ b/codex-rs/protocol/src/approvals.rs
@@ -52,6 +52,7 @@ pub struct ExecApprovalRequestEvent {
     pub risk: Option<SandboxCommandAssessment>,
     /// Prefix rule that can be added to the user's execpolicy to allow future runs.
     #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[ts(optional, type = "Array<string>")]
     pub allow_prefix: Option<Vec<String>>,
     pub parsed_cmd: Vec<ParsedCommand>,
 }