diff --git a/src/doc/guide-unsafe.md b/src/doc/guide-unsafe.md
index 8c67634d57aec..ba79e828150e5 100644
--- a/src/doc/guide-unsafe.md
+++ b/src/doc/guide-unsafe.md
@@ -573,8 +573,8 @@ pub extern fn dot_product(a: *const u32, a_len: u32,
     return ret;
 }
 
-#[lang = "begin_unwind"]
-extern fn begin_unwind(args: &core::fmt::Arguments,
+#[lang = "fail_fmt"]
+extern fn fail_fmt(args: &core::fmt::Arguments,
                        file: &str,
                        line: uint) -> ! {
     loop {}
@@ -587,8 +587,8 @@ extern fn begin_unwind(args: &core::fmt::Arguments,
 ```
 
 Note that there is one extra lang item here which differs from the examples
-above, `begin_unwind`. This must be defined by consumers of libcore because the
-core library declares failure, but it does not define it. The `begin_unwind`
+above, `fail_fmt`. This must be defined by consumers of libcore because the
+core library declares failure, but it does not define it. The `fail_fmt`
 lang item is this crate's definition of failure, and it must be guaranteed to
 never return.
 
@@ -706,7 +706,7 @@ Other features provided by lang items include:
   `==`, `<`, dereferencing (`*`) and `+` (etc.) operators are all
   marked with lang items; those specific four are `eq`, `ord`,
   `deref`, and `add` respectively.
-- stack unwinding and general failure; the `eh_personality`, `fail_`
+- stack unwinding and general failure; the `eh_personality`, `fail`
   and `fail_bounds_checks` lang items.
 - the traits in `std::kinds` used to indicate types that satisfy
   various kinds; lang items `send`, `sync` and `copy`.
diff --git a/src/libcore/failure.rs b/src/libcore/failure.rs
index ac162c206c68c..f5f45b2f72e2a 100644
--- a/src/libcore/failure.rs
+++ b/src/libcore/failure.rs
@@ -16,7 +16,7 @@
 //! interface for failure is:
 //!
 //! ```ignore
-//! fn begin_unwind(fmt: &fmt::Arguments, &(&'static str, uint)) -> !;
+//! fn fail_impl(fmt: &fmt::Arguments, &(&'static str, uint)) -> !;
 //! ```
 //!
 //! This definition allows for failing with any general message, but it does not
@@ -33,13 +33,28 @@
 use fmt;
 use intrinsics;
 
+// NOTE: remove after next snapshot
+#[cfg(stage0)]
 #[cold] #[inline(never)] // this is the slow path, always
 #[lang="fail_"]
 fn fail_(expr_file_line: &(&'static str, &'static str, uint)) -> ! {
     let (expr, file, line) = *expr_file_line;
     let ref file_line = (file, line);
     format_args!(|args| -> () {
-        begin_unwind(args, file_line);
+        fail_fmt(args, file_line);
+    }, "{}", expr);
+
+    unsafe { intrinsics::abort() }
+}
+
+#[cfg(not(stage0))]
+#[cold] #[inline(never)] // this is the slow path, always
+#[lang="fail"]
+fn fail(expr_file_line: &(&'static str, &'static str, uint)) -> ! {
+    let (expr, file, line) = *expr_file_line;
+    let ref file_line = (file, line);
+    format_args!(|args| -> () {
+        fail_fmt(args, file_line);
     }, "{}", expr);
 
     unsafe { intrinsics::abort() }
@@ -50,25 +65,33 @@ fn fail_(expr_file_line: &(&'static str, &'static str, uint)) -> ! {
 fn fail_bounds_check(file_line: &(&'static str, uint),
                      index: uint, len: uint) -> ! {
     format_args!(|args| -> () {
-        begin_unwind(args, file_line);
+        fail_fmt(args, file_line);
     }, "index out of bounds: the len is {} but the index is {}", len, index);
     unsafe { intrinsics::abort() }
 }
 
 #[cold] #[inline(never)]
-pub fn begin_unwind_string(msg: &str, file: &(&'static str, uint)) -> ! {
-    format_args!(|fmt| begin_unwind(fmt, file), "{}", msg)
+pub fn fail_str(msg: &str, file: &(&'static str, uint)) -> ! {
+    format_args!(|fmt| fail_fmt(fmt, file), "{}", msg)
 }
 
 #[cold] #[inline(never)]
-pub fn begin_unwind(fmt: &fmt::Arguments, file_line: &(&'static str, uint)) -> ! {
+pub fn fail_fmt(fmt: &fmt::Arguments, file_line: &(&'static str, uint)) -> ! {
     #[allow(ctypes)]
     extern {
+
+        // NOTE: remove after next snapshot
+        #[cfg(stage0)]
         #[lang = "begin_unwind"]
-        fn begin_unwind(fmt: &fmt::Arguments, file: &'static str,
+        fn fail_impl(fmt: &fmt::Arguments, file: &'static str,
                         line: uint) -> !;
+
+        #[cfg(not(stage0))]
+        #[lang = "fail_fmt"]
+        fn fail_impl(fmt: &fmt::Arguments, file: &'static str,
+                        line: uint) -> !;
+
     }
     let (file, line) = *file_line;
-    unsafe { begin_unwind(fmt, file, line) }
+    unsafe { fail_impl(fmt, file, line) }
 }
-
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index e846f8dbeb404..0f972a6702916 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -18,7 +18,7 @@ macro_rules! fail(
     );
     ($msg:expr) => ({
         static _FILE_LINE: (&'static str, uint) = (file!(), line!());
-        ::core::failure::begin_unwind_string($msg, &_FILE_LINE)
+        ::core::failure::fail_str($msg, &_FILE_LINE)
     });
     ($fmt:expr, $($arg:tt)*) => ({
         // a closure can't have return type !, so we need a full
@@ -40,7 +40,7 @@ macro_rules! fail(
         #[inline(always)]
         fn _run_fmt(fmt: &::std::fmt::Arguments) -> ! {
             static _FILE_LINE: (&'static str, uint) = (file!(), line!());
-            ::core::failure::begin_unwind(fmt, &_FILE_LINE)
+            ::core::failure::fail_fmt(fmt, &_FILE_LINE)
         }
         format_args!(_run_fmt, $fmt, $($arg)*)
     });
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index daba3b701c03b..50c92b45fdff4 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -264,7 +264,7 @@ lets_do_this! {
 
     StrEqFnLangItem,                 "str_eq",                  str_eq_fn;
 
-    // A number of failure-related lang items. The `fail_` item corresponds to
+    // A number of failure-related lang items. The `fail` item corresponds to
     // divide-by-zero and various failure cases with `match`. The
     // `fail_bounds_check` item is for indexing arrays.
     //
@@ -273,9 +273,9 @@ lets_do_this! {
     // defined to use it, but a final product is required to define it
     // somewhere. Additionally, there are restrictions on crates that use a weak
     // lang item, but do not have it defined.
-    FailFnLangItem,                  "fail_",                   fail_fn;
+    FailFnLangItem,                  "fail",                    fail_fn;
     FailBoundsCheckFnLangItem,       "fail_bounds_check",       fail_bounds_check_fn;
-    BeginUnwindLangItem,             "begin_unwind",            begin_unwind;
+    FailFmtLangItem,                 "fail_fmt",                fail_fmt;
 
     ExchangeMallocFnLangItem,        "exchange_malloc",         exchange_malloc_fn;
     ExchangeFreeFnLangItem,          "exchange_free",           exchange_free_fn;
diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
index 81099da3fac05..79faf3aa147ed 100644
--- a/src/librustc/middle/weak_lang_items.rs
+++ b/src/librustc/middle/weak_lang_items.rs
@@ -118,7 +118,7 @@ impl<'a, 'v> Visitor<'v> for Context<'a> {
 ) )
 
 weak_lang_items!(
-    begin_unwind,       BeginUnwindLangItem,        rust_begin_unwind;
+    fail_fmt,           FailFmtLangItem,            rust_begin_unwind;
     stack_exhausted,    StackExhaustedLangItem,     rust_stack_exhausted;
     eh_personality,     EhPersonalityLangItem,      rust_eh_personality;
 )
diff --git a/src/librustrt/unwind.rs b/src/librustrt/unwind.rs
index acef05e08673b..034ed470c9752 100644
--- a/src/librustrt/unwind.rs
+++ b/src/librustrt/unwind.rs
@@ -488,7 +488,16 @@ pub mod eabi {
 }
 
 // Entry point of failure from the libcore crate
-#[cfg(not(test))]
+#[cfg(not(test), not(stage0))]
+#[lang = "fail_fmt"]
+pub extern fn rust_begin_unwind(msg: &fmt::Arguments,
+                                file: &'static str, line: uint) -> ! {
+    begin_unwind_fmt(msg, &(file, line))
+}
+
+//
+// Entry point of failure from the libcore crate
+#[cfg(stage0, not(test))]
 #[lang = "begin_unwind"]
 pub extern fn rust_begin_unwind(msg: &fmt::Arguments,
                                 file: &'static str, line: uint) -> ! {
diff --git a/src/test/auxiliary/lang-item-public.rs b/src/test/auxiliary/lang-item-public.rs
index 5723b59a60b95..73bad01147240 100644
--- a/src/test/auxiliary/lang-item-public.rs
+++ b/src/test/auxiliary/lang-item-public.rs
@@ -11,7 +11,7 @@
 #![no_std]
 #![feature(lang_items)]
 
-#[lang="fail_"]
+#[lang="fail"]
 fn fail(_: &(&'static str, &'static str, uint)) -> ! { loop {} }
 
 #[lang = "stack_exhausted"]
diff --git a/src/test/compile-fail/lint-dead-code-1.rs b/src/test/compile-fail/lint-dead-code-1.rs
index 3e563e9e13806..b7feea775cb43 100644
--- a/src/test/compile-fail/lint-dead-code-1.rs
+++ b/src/test/compile-fail/lint-dead-code-1.rs
@@ -108,5 +108,5 @@ fn g() { h(); }
 fn h() {}
 
 // Similarly, lang items are live
-#[lang="fail_"]
+#[lang="fail"]
 fn fail(_: *const u8, _: *const u8, _: uint) -> ! { loop {} }
diff --git a/src/test/compile-fail/weak-lang-item.rs b/src/test/compile-fail/weak-lang-item.rs
index 636adefb95e27..74ec56f7bd90a 100644
--- a/src/test/compile-fail/weak-lang-item.rs
+++ b/src/test/compile-fail/weak-lang-item.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // aux-build:weak-lang-items.rs
-// error-pattern: language item required, but not found: `begin_unwind`
+// error-pattern: language item required, but not found: `fail_fmt`
 // error-pattern: language item required, but not found: `stack_exhausted`
 // error-pattern: language item required, but not found: `eh_personality`