diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 6ef64ef3d96d91401240b3c59f81ad887c79d478..36b74cbcb4f7cc1cbb9916dd7971977843275a5c 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -864,7 +864,8 @@ fn parse_optimization_fuel(slot: &mut Option<(String, u64)>, v: Option<&str>) ->
          build_codegen_options, "C", "codegen",
          CG_OPTIONS, cg_type_desc, cgsetters,
     ar: Option<String> = (None, parse_opt_string, [UNTRACKED],
-        "tool to assemble archives with"),
+        "tool to assemble archives with (has no effect currently, \
+         rustc doesn't use an external archiver)"),
     linker: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "system linker to link outputs with"),
     link_arg: Vec<String> = (vec![], parse_string_push, [UNTRACKED],