diff --git a/build_test/CHANGELOG.md b/build_test/CHANGELOG.md
index 958529e29..2ce9d9074 100644
--- a/build_test/CHANGELOG.md
+++ b/build_test/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.2.1-dev
+
+- Avoid passing a nullable value to `Future.value`.
+
 ## 2.2.0
 
 - Forward logs from `testBuilder` to `printOnFailure` by default.
diff --git a/build_test/lib/src/written_asset_reader.dart b/build_test/lib/src/written_asset_reader.dart
index a9c9e3eb1..52db3fbe1 100644
--- a/build_test/lib/src/written_asset_reader.dart
+++ b/build_test/lib/src/written_asset_reader.dart
@@ -51,7 +51,7 @@ class WrittenAssetReader extends MultiPackageAssetReader {
     if (!source.assets.containsKey(id)) {
       throw AssetNotFoundException(id);
     }
-    return Future.value(source.assets[id]);
+    return Future.value(source.assets[id]!);
   }
 
   @override
diff --git a/build_test/pubspec.yaml b/build_test/pubspec.yaml
index d0081491d..29c3cb446 100644
--- a/build_test/pubspec.yaml
+++ b/build_test/pubspec.yaml
@@ -1,6 +1,6 @@
 name: build_test
 description: Utilities for writing unit tests of Builders.
-version: 2.2.0
+version: 2.2.1-dev
 repository: https://github.com/dart-lang/build/tree/master/build_test
 
 environment: