diff --git a/.gitignore b/.gitignore
index c8962ef..8e2af0e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 /libcxx-3.8.1.src.tar.xz
 /libcxx-3.9.0.src.tar.xz
 /libcxx-3.9.1.src.tar.xz
+/libcxx-4.0.0.src.tar.xz
diff --git a/libcxx.spec b/libcxx.spec
index ec70ecd..1684eaf 100644
--- a/libcxx.spec
+++ b/libcxx.spec
@@ -3,7 +3,7 @@
 %global bootstrap 0
 
 Name:		libcxx
-Version:	3.9.1
+Version:	4.0.0
 Release:	1%{?dist}
 Summary:	C++ standard library targeting C++11
 License:	MIT or NCSA
@@ -98,6 +98,9 @@ make install DESTDIR=%{buildroot}
 %{_libdir}/libc++.so
 
 %changelog
+* Sat Apr 22 2017 Tom Callaway <spot@fedoraproject.org> - 4.0.0-1
+- update to 4.0.0
+
 * Wed Mar  8 2017 Tom Callaway <spot@fedoraproject.org> - 3.9.1-1
 - update to 3.9.1
 
diff --git a/sources b/sources
index 268f724..739e1cd 100644
--- a/sources
+++ b/sources
@@ -1 +1 @@
-SHA512 (libcxx-3.9.1.src.tar.xz) = a5976e4096624a7307b3e43f4a22ac2dc74572226e0f57af9f3ef537a14c3cff1601b7042aef9dc40a0ee53ca76b08d72eb9c253dcf34f115d3153c302db7070
+SHA512 (libcxx-4.0.0.src.tar.xz) = 6dad794c00919955e14710def169cdcde8a1743431479e993c4a6a3c87c2fd9f5dbd6e17542e524981eed0783dce70384c356b74ef3c6d70598c6ff03454b1dd