diff --git a/src/librustc/lib/llvm.rs b/src/librustc/lib/llvm.rs
index 14af20f0cb9..160bc511168 100644
--- a/src/librustc/lib/llvm.rs
+++ b/src/librustc/lib/llvm.rs
@@ -33,6 +33,7 @@ pub enum CallConv {
     ColdCallConv = 9,
     X86StdcallCallConv = 64,
     X86FastcallCallConv = 65,
+    X86_64_Win64 = 79,
 }
 
 pub enum Visibility {
diff --git a/src/librustc/middle/trans/foreign.rs b/src/librustc/middle/trans/foreign.rs
index 7da80507df0..161c4ee0d14 100644
--- a/src/librustc/middle/trans/foreign.rs
+++ b/src/librustc/middle/trans/foreign.rs
@@ -33,7 +33,7 @@ use syntax::{ast};
 use syntax::{attr, ast_map};
 use syntax::parse::token::special_idents;
 use syntax::abi::{RustIntrinsic, Rust, Stdcall, Fastcall, System,
-                  Cdecl, Aapcs, C, AbiSet};
+                  Cdecl, Aapcs, C, AbiSet, Win64};
 use util::ppaux::{Repr, UserString};
 use middle::trans::type_::Type;
 
@@ -96,6 +96,7 @@ pub fn llvm_calling_convention(ccx: &mut CrateContext,
             Stdcall => lib::llvm::X86StdcallCallConv,
             Fastcall => lib::llvm::X86FastcallCallConv,
             C => lib::llvm::CCallConv,
+            Win64 => lib::llvm::X86_64_Win64,
 
             // NOTE These API constants ought to be more specific
             Cdecl => lib::llvm::CCallConv,
diff --git a/src/libsyntax/abi.rs b/src/libsyntax/abi.rs
index 972d2f43e73..4e9ba5532f3 100644
--- a/src/libsyntax/abi.rs
+++ b/src/libsyntax/abi.rs
@@ -23,6 +23,7 @@ pub enum Abi {
     Stdcall,
     Fastcall,
     Aapcs,
+    Win64,
 
     // Multiplatform ABIs second
     Rust,
@@ -73,6 +74,8 @@ static AbiDatas: &'static [AbiData] = &[
     AbiData {abi: Stdcall, name: "stdcall", abi_arch: Archs(IntelBits)},
     AbiData {abi: Fastcall, name:"fastcall", abi_arch: Archs(IntelBits)},
     AbiData {abi: Aapcs, name: "aapcs", abi_arch: Archs(ArmBits)},
+    AbiData {abi: Win64, name: "win64",
+             abi_arch: Archs(1 << (X86_64 as uint))},
 
     // Cross-platform ABIs
     //
diff --git a/src/test/auxiliary/extern_calling_convention.rs b/src/test/auxiliary/extern_calling_convention.rs
new file mode 100644
index 00000000000..30579f0fc77
--- /dev/null
+++ b/src/test/auxiliary/extern_calling_convention.rs
@@ -0,0 +1,27 @@
+// Copyright 2013 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.
+
+// Make sure Rust generates the correct calling convention for extern
+// functions.
+
+#[inline(never)]
+pub extern "win64" fn foo(a: int, b: int, c: int, d: int) {
+    assert!(a == 1);
+    assert!(b == 2);
+    assert!(c == 3);
+    assert!(d == 4);
+    
+    println!("a: {:?}, b: {:?}, c: {:?}, d: {:?}",
+             a, b, c, d)
+}
+
+fn main() {
+    foo(1, 2, 3, 4)
+}
diff --git a/src/test/run-pass/extern-calling-convention-test.rs b/src/test/run-pass/extern-calling-convention-test.rs
new file mode 100644
index 00000000000..e8609a8b60b
--- /dev/null
+++ b/src/test/run-pass/extern-calling-convention-test.rs
@@ -0,0 +1,20 @@
+// Copyright 2013 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.
+
+// xfail-fast: aux-build not compatible with fast
+// aux-build:extern_calling_convention.rs
+
+extern mod extern_calling_convention;
+
+use extern_calling_convention::foo;
+
+fn main() {
+    foo(1, 2, 3, 4);
+}