diff --git a/llvm/utils/gn/secondary/libcxx/config.gni b/llvm/utils/gn/secondary/libcxx/config.gni
index b90263a1f90323..9e49db1dcc8cea 100644
--- a/llvm/utils/gn/secondary/libcxx/config.gni
+++ b/llvm/utils/gn/secondary/libcxx/config.gni
@@ -1,10 +1,7 @@
 declare_args() {
-  # ABI version of libc++. Can be either 1 or 2, where 2 is currently not stable. Defaults to 1.
+  # libc++ ABI version. Either 1 (default) or 2 (unstable).
   libcxx_abi_version = 1
 
-  # The inline ABI namespace used by libc++. It defaults to __n where `n` is the current ABI version.
+  # libc++ inline ABI namespace. Defaults to __n, where n is the ABI version.
   libcxx_abi_namespace = ""
-
-  # Unstable ABI of libc++.
-  libcxx_abi_unstable = false
 }
diff --git a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
index ec7794a0804177..e0ddd12b28e183 100644
--- a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
@@ -50,11 +50,6 @@ if (current_toolchain == default_toolchain) {
     } else {
       values += [ "_LIBCPP_ABI_NAMESPACE=" ]
     }
-    if (libcxx_abi_unstable) {
-      values += [ "_LIBCPP_ABI_UNSTABLE=1" ]
-    } else {
-      values += [ "_LIBCPP_ABI_UNSTABLE=" ]
-    }
   }
 
   copy("copy_headers") {