diff --git a/Cargo.lock b/Cargo.lock
index fd4b8f3e16ca..59505ff7ed7f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3469,6 +3469,7 @@ name = "rustc_index"
 version = "0.0.0"
 dependencies = [
  "serialize",
+ "smallvec",
 ]
 
 [[package]]
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index a9ef297fa991..e28ee48201c8 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -37,7 +37,7 @@ extern crate libc;
 extern crate cfg_if;
 
 pub use rustc_serialize::hex::ToHex;
-pub use rustc_index::{indexed_vec, newtype_index};
+pub use rustc_index::{bit_set, indexed_vec, newtype_index};
 
 #[inline(never)]
 #[cold]
@@ -69,7 +69,6 @@ pub mod macros;
 pub mod svh;
 pub mod base_n;
 pub mod binary_search_util;
-pub mod bit_set;
 pub mod box_region;
 pub mod const_cstr;
 pub mod flock;
diff --git a/src/librustc_index/Cargo.toml b/src/librustc_index/Cargo.toml
index 10e66ffe5906..b1ebc95e4881 100644
--- a/src/librustc_index/Cargo.toml
+++ b/src/librustc_index/Cargo.toml
@@ -11,3 +11,4 @@ doctest = false
 
 [dependencies]
 rustc_serialize = { path = "../libserialize", package = "serialize" }
+smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
diff --git a/src/librustc_data_structures/bit_set.rs b/src/librustc_index/bit_set.rs
similarity index 100%
rename from src/librustc_data_structures/bit_set.rs
rename to src/librustc_index/bit_set.rs
diff --git a/src/librustc_data_structures/bit_set/tests.rs b/src/librustc_index/bit_set/tests.rs
similarity index 100%
rename from src/librustc_data_structures/bit_set/tests.rs
rename to src/librustc_index/bit_set/tests.rs
diff --git a/src/librustc_index/lib.rs b/src/librustc_index/lib.rs
index c4c4948e7bf5..d70f51aec01e 100644
--- a/src/librustc_index/lib.rs
+++ b/src/librustc_index/lib.rs
@@ -3,3 +3,4 @@
 #![feature(fn_traits)]
 
 pub mod indexed_vec;
+pub mod bit_set;