diff --git a/src/librustc_back/lib.rs b/src/librustc_back/lib.rs
index 5db6c729755..e48f9df7564 100644
--- a/src/librustc_back/lib.rs
+++ b/src/librustc_back/lib.rs
@@ -36,8 +36,6 @@
 #[phase(plugin, link)]
 extern crate log;
 extern crate syntax;
-extern crate libc;
-extern crate flate;
 extern crate serialize;
 
 pub mod abi;
diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index c026a1c97c1..78d3d86b296 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-extern crate libc;
-
 use codemap::{Pos, Span};
 use codemap;
 use diagnostics;