diff --git a/BUILD.gn b/BUILD.gn
index 3ff8e03ad7d..80e3bdd3757 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -74,7 +74,8 @@ group("create_sdk") {
   ]
 }
 
-if (dart_host_sdk_toolchain != host_toolchain) {
+if (defined(dart_host_sdk_toolchain) &&
+    dart_host_sdk_toolchain != host_toolchain) {
   group("create_host_sdk") {
     deps = [
       "sdk:create_sdk($dart_host_sdk_toolchain)",
diff --git a/build/dart_host_sdk_toolchain.gni b/build/dart_host_sdk_toolchain.gni
index 95005db5eaf..f61d287ff81 100644
--- a/build/dart_host_sdk_toolchain.gni
+++ b/build/dart_host_sdk_toolchain.gni
@@ -2,17 +2,15 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-declare_args() {
-  # In a cross-build, this should be set to the toolchain to use to build a Dart
-  # SDK to run on the host that targets the host. This is distinct from
-  # 'host_toolchain', which in a cross-build builds artifacts to run on the host
-  # that target the target architecture.
-  dart_host_sdk_toolchain = host_toolchain
-}
-
 # dart_host_toolchain should be used in the Dart tree instead of host_toolchain.
 # It will ensure that we are selecting the correct host toolchain.
 dart_host_toolchain = host_toolchain
-if (current_toolchain == dart_host_sdk_toolchain) {
+
+# Config variable: dart_host_sdk_toolchain
+# In a cross-build, this should be set to the toolchain to use to build a Dart
+# SDK to run on the host that targets the host. This is distinct from
+# 'host_toolchain', which in a cross-build builds artifacts to run on the host
+# that target the target architecture.
+if (defined(dart_host_sdk_toolchain) && current_toolchain == dart_host_sdk_toolchain) {
   dart_host_toolchain = dart_host_sdk_toolchain
 }