diff --git a/compiler/rustc_serialize/src/opaque.rs b/compiler/rustc_serialize/src/opaque.rs
index 81f6266f8d1..0a55504a556 100644
--- a/compiler/rustc_serialize/src/opaque.rs
+++ b/compiler/rustc_serialize/src/opaque.rs
@@ -19,7 +19,7 @@ pub type FileEncodeResult = Result<usize, (PathBuf, io::Error)>;
 pub const MAGIC_END_BYTES: &[u8] = b"rust-end-file";
 
 /// The size of the buffer in `FileEncoder`.
-const BUF_SIZE: usize = 8192;
+const BUF_SIZE: usize = 64 * 1024;
 
 /// `FileEncoder` encodes data to file via fixed-size buffer.
 ///