diff --git a/src/libsyntax_ext/proc_macro_registrar.rs b/src/libsyntax_ext/proc_macro_registrar.rs
index 8c5276e1d74b5..0ba21e6b366cf 100644
--- a/src/libsyntax_ext/proc_macro_registrar.rs
+++ b/src/libsyntax_ext/proc_macro_registrar.rs
@@ -381,7 +381,7 @@ fn mk_registrar(cx: &mut ExtCtxt,
 
     let __internal = Ident::from_str("__internal");
     let registry = Ident::from_str("Registry");
-    let registrar = Ident::from_str("registrar");
+    let registrar = Ident::from_str("_registrar");
     let register_custom_derive = Ident::from_str("register_custom_derive");
     let register_attr_proc_macro = Ident::from_str("register_attr_proc_macro");
     let register_bang_proc_macro = Ident::from_str("register_bang_proc_macro");
diff --git a/src/test/run-pass-fulldeps/proc-macro/auxiliary/empty-crate.rs b/src/test/run-pass-fulldeps/proc-macro/auxiliary/empty-crate.rs
new file mode 100644
index 0000000000000..b45d4bf41d635
--- /dev/null
+++ b/src/test/run-pass-fulldeps/proc-macro/auxiliary/empty-crate.rs
@@ -0,0 +1,14 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![deny(unused_variables)]
diff --git a/src/test/run-pass-fulldeps/proc-macro/empty-crate.rs b/src/test/run-pass-fulldeps/proc-macro/empty-crate.rs
new file mode 100644
index 0000000000000..38a2716aee77b
--- /dev/null
+++ b/src/test/run-pass-fulldeps/proc-macro/empty-crate.rs
@@ -0,0 +1,17 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:empty-crate.rs
+// ignore-stage1
+
+#[macro_use]
+extern crate empty_crate;
+
+fn main() {}