diff --git a/lib/types/aux-user-types.js b/lib/types/aux-user-types.js
new file mode 100644
--- /dev/null
+++ b/lib/types/aux-user-types.js
@@ -0,0 +1,9 @@
+// @flow
+
+export type AuxUserInfo = { +fid: string };
+
+export type AuxUserInfos = { +[userID: string]: AuxUserInfo };
+
+export type AuxUserStore = {
+  +auxUserInfos: AuxUserInfos,
+};