diff --git a/third_party/libc++abi/BUILD.gn b/third_party/libc++abi/BUILD.gn
index 010098a..7399788 100644
--- a/third_party/libc++abi/BUILD.gn
+++ b/third_party/libc++abi/BUILD.gn
@@ -28,8 +28,8 @@
     "trunk/src/stdlib_stdexcept.cpp",
     "trunk/src/stdlib_typeinfo.cpp",
   ]
-  if (is_linux && !is_mac) {
-    sources == [ "trunk/src/cxa_thread_atexit.cpp" ]
+  if (is_posix && !is_mac) {
+    sources += [ "trunk/src/cxa_thread_atexit.cpp" ]
   }
   configs -= [
     "//build/config/compiler:chromium_code",