diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index b95aae02894..5f90e28cb3c 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -63,7 +63,7 @@ use core::ops::Bound::{Excluded, Included, Unbounded};
 use core::ops::{self, Add, AddAssign, Index, IndexMut, RangeBounds};
 use core::ptr;
 use core::str::pattern::Pattern;
-use std_unicode::lossy;
+use core::str::lossy;
 use std_unicode::char::{decode_utf16, REPLACEMENT_CHARACTER};
 
 use borrow::{Cow, ToOwned};
diff --git a/src/libstd_unicode/lossy.rs b/src/libcore/str/lossy.rs
similarity index 98%
rename from src/libstd_unicode/lossy.rs
rename to src/libcore/str/lossy.rs
index cc8e93308a5..30b7267da7c 100644
--- a/src/libstd_unicode/lossy.rs
+++ b/src/libcore/str/lossy.rs
@@ -8,12 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use core::str as core_str;
-use core::fmt;
-use core::fmt::Write;
 use char;
-use core::mem;
-
+use str as core_str;
+use fmt;
+use fmt::Write;
+use mem;
 
 /// Lossy UTF-8 string.
 #[unstable(feature = "str_internals", issue = "0")]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 1185b7acaae..7a97d89dcf9 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -26,6 +26,10 @@ use mem;
 
 pub mod pattern;
 
+#[unstable(feature = "str_internals", issue = "0")]
+#[allow(missing_docs)]
+pub mod lossy;
+
 /// A trait to abstract the idea of creating a new instance of a type from a
 /// string.
 ///
diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index c3162899bbd..149269263dc 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -33,6 +33,7 @@
 #![feature(sort_internals)]
 #![feature(specialization)]
 #![feature(step_trait)]
+#![feature(str_internals)]
 #![feature(test)]
 #![feature(trusted_len)]
 #![feature(try_trait)]
@@ -68,4 +69,5 @@ mod ptr;
 mod result;
 mod slice;
 mod str;
+mod str_lossy;
 mod tuple;
diff --git a/src/libstd_unicode/tests/lossy.rs b/src/libcore/tests/str_lossy.rs
similarity index 99%
rename from src/libstd_unicode/tests/lossy.rs
rename to src/libcore/tests/str_lossy.rs
index e05d0668556..69e28256da9 100644
--- a/src/libstd_unicode/tests/lossy.rs
+++ b/src/libcore/tests/str_lossy.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std_unicode::lossy::*;
+use core::str::lossy::*;
 
 #[test]
 fn chunks() {
diff --git a/src/libstd/sys/redox/os_str.rs b/src/libstd/sys/redox/os_str.rs
index da27787babb..eb3a1ead58c 100644
--- a/src/libstd/sys/redox/os_str.rs
+++ b/src/libstd/sys/redox/os_str.rs
@@ -19,7 +19,7 @@ use rc::Rc;
 use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use sys_common::bytestring::debug_fmt_bytestring;
-use std_unicode::lossy::Utf8Lossy;
+use core::str::lossy::Utf8Lossy;
 
 #[derive(Clone, Hash)]
 pub struct Buf {
diff --git a/src/libstd/sys/unix/os_str.rs b/src/libstd/sys/unix/os_str.rs
index e43bc6da5f1..01c0fb830aa 100644
--- a/src/libstd/sys/unix/os_str.rs
+++ b/src/libstd/sys/unix/os_str.rs
@@ -19,7 +19,7 @@ use rc::Rc;
 use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use sys_common::bytestring::debug_fmt_bytestring;
-use std_unicode::lossy::Utf8Lossy;
+use core::str::lossy::Utf8Lossy;
 
 #[derive(Clone, Hash)]
 pub struct Buf {
diff --git a/src/libstd/sys/wasm/os_str.rs b/src/libstd/sys/wasm/os_str.rs
index 84f560af69b..e0da5bdf36c 100644
--- a/src/libstd/sys/wasm/os_str.rs
+++ b/src/libstd/sys/wasm/os_str.rs
@@ -19,7 +19,7 @@ use rc::Rc;
 use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use sys_common::bytestring::debug_fmt_bytestring;
-use std_unicode::lossy::Utf8Lossy;
+use core::str::lossy::Utf8Lossy;
 
 #[derive(Clone, Hash)]
 pub struct Buf {
diff --git a/src/libstd/sys_common/bytestring.rs b/src/libstd/sys_common/bytestring.rs
index eb9cad09915..971b83938c1 100644
--- a/src/libstd/sys_common/bytestring.rs
+++ b/src/libstd/sys_common/bytestring.rs
@@ -11,7 +11,7 @@
 #![allow(dead_code)]
 
 use fmt::{Formatter, Result, Write};
-use std_unicode::lossy::{Utf8Lossy, Utf8LossyChunk};
+use core::str::lossy::{Utf8Lossy, Utf8LossyChunk};
 
 pub fn debug_fmt_bytestring(slice: &[u8], f: &mut Formatter) -> Result {
     // Writes out a valid unicode string with the correct escape sequences
diff --git a/src/libstd_unicode/Cargo.toml b/src/libstd_unicode/Cargo.toml
index 283070a0e2c..b1c55c2e4b6 100644
--- a/src/libstd_unicode/Cargo.toml
+++ b/src/libstd_unicode/Cargo.toml
@@ -9,10 +9,6 @@ path = "lib.rs"
 test = false
 bench = false
 
-[[test]]
-name = "std_unicode_tests"
-path = "tests/lib.rs"
-
 [dependencies]
 core = { path = "../libcore" }
 compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/libstd_unicode/lib.rs b/src/libstd_unicode/lib.rs
index cf8c101a2f9..106a2c0f0c5 100644
--- a/src/libstd_unicode/lib.rs
+++ b/src/libstd_unicode/lib.rs
@@ -45,7 +45,6 @@ mod tables;
 mod u_str;
 mod version;
 pub mod char;
-pub mod lossy;
 
 #[allow(deprecated)]
 pub mod str {
diff --git a/src/libstd_unicode/tests/lib.rs b/src/libstd_unicode/tests/lib.rs
deleted file mode 100644
index 9535ec18763..00000000000
--- a/src/libstd_unicode/tests/lib.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright 2012-2017 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.
-
-#![feature(str_internals, unicode)]
-
-extern crate std_unicode;
-
-mod lossy;