diff --git a/src/server/auth/types.ts b/src/server/auth/types.ts
index 93c5a493..cd1430f1 100644
--- a/src/server/auth/types.ts
+++ b/src/server/auth/types.ts
@@ -21,4 +21,9 @@ export interface AuthInfo {
    * When the token expires (in seconds since epoch).
    */
   expiresAt?: number;
+
+  /**
+   * Additional arbitrary properties that may be included.
+   */
+  [key: string]: unknown;
 }
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