diff --git a/zx b/zx
index 9b711fa..437f0cd 100755
--- a/zx
+++ b/zx
@@ -1834,6 +1834,12 @@ fetch(Socket, PackageID) ->
     log(info, "Fetched ~ts", [package_string(LatestID)]).
 
 
+-spec request_zrp(Socket, PackageID) -> Result
+    when Socket :: gen_tcp:socket(),
+         PackageID :: package_id(),
+         Result    :: {ok, Latest :: package_id()}
+                    | {error, Reason :: timeout | term()}.
+
 request_zrp(Socket, PackageID) ->
     ok = send(Socket, {fetch, PackageID}),
     receive
@@ -1852,6 +1858,11 @@ request_zrp(Socket, PackageID) ->
    end.
 
 
+-spec receive_zrp(Socket, PackageID) -> Result
+    when Socket    :: gen_tcp:socket(),
+         PackageID :: package_id(),
+         Result    :: ok | {error, timeout}.
+
 receive_zrp(Socket, PackageID) ->
     receive
         {tcp, Socket, Bin} ->