diff --git a/.travis.yml b/.travis.yml
index ed130f2..d412cc2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,9 +4,6 @@
   - dev
   - stable
   - 1.22.1
-  - 1.21.1
-  - 1.20.1
-  - 1.19.1
 
 dart_task:
   - test: --platform vm
@@ -27,18 +24,6 @@
       dart_task: dartanalyzer
     - dart: stable
       dart_task: dartanalyzer
-  exclude:
-    # Exclude Firefox tests on SDKs before 1.22.0-dev.4 which are lacking fix
-    # https://github.com/dart-lang/sdk/commit/7c3c297a8ad907f12bf12b96a21777421067fd18
-    - dart: 1.21.1
-      dart_task:
-        test: --platform firefox -j 1
-    - dart: 1.20.1
-      dart_task:
-        test: --platform firefox -j 1
-    - dart: 1.19.1
-      dart_task:
-        test: --platform firefox -j 1
 
 # Only building master means that we don't run two builds for each pull request.
 branches:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9246811..dc3c6cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 0.7.0
+
+* Give a return type to the `Handler` typedef. This may cause static warnings
+  where there previously were none, but all handlers should have already been
+  returning a `Response` or `Future<Response>`.
+
 ## 0.6.8
 
 * Add a `securityContext` parameter to `self_io.serve()`.
diff --git a/lib/src/handler.dart b/lib/src/handler.dart
index 4bb08e9..8ff2a89 100644
--- a/lib/src/handler.dart
+++ b/lib/src/handler.dart
@@ -1,14 +1,21 @@
 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // 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.
+import 'dart:async';
 
 import 'request.dart';
+import 'response.dart';
 
-/// The signature of a function which handles a [Request].
+/// A function which handles a [Request].
+///
+/// For example a static file handler may read the requested URI from the
+/// filesystem and return it as the body of the [Response].
+///
+/// A [Handler] which wraps one or more other handlers to perform pre or post
+/// processing is knowns as a "middleware".
 ///
 /// A [Handler] may receive a request directly from an HTTP server or it
-/// may be composed as part of a larger application.
-///
-/// Should return [Response] or [Future<Response>].
-//TODO(kevmoo): provide a more detailed explanation.
-typedef Handler(Request request);
+/// may have been touched by other middleware. Similarly the response may be
+/// directly returned by an HTTP server or have further processing done by other
+/// middleware.
+typedef FutureOr<Response> Handler(Request request);
diff --git a/pubspec.yaml b/pubspec.yaml
index 4ae3c8a..8d5281c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,10 +1,10 @@
 name: shelf
-version: 0.6.9-dev
+version: 0.7.0-dev
 author: Dart Team <misc@dartlang.org>
 description: Web Server Middleware for Dart
 homepage: https://github.com/dart-lang/shelf
 environment:
-  sdk: '>=1.13.2 <2.0.0-dev.infinity'
+  sdk: '>=1.22.0 <2.0.0-dev.infinity'
 dependencies:
   async: '^1.10.0'
   collection: '^1.5.0'
@@ -14,5 +14,5 @@
   stream_channel: '^1.0.0'
 dev_dependencies:
   http: '>=0.9.2 <0.12.0'
-  scheduled_test: '^0.12.0'
-  test: '^0.12.7'
+  scheduled_test: '^0.12.11'
+  test: '^0.12.20'
diff --git a/test/create_middleware_test.dart b/test/create_middleware_test.dart
index bb4b245..c17bcab 100644
--- a/test/create_middleware_test.dart
+++ b/test/create_middleware_test.dart
@@ -230,7 +230,10 @@
   });
 }
 
-_failHandler(Request request) => fail('should never get here');
+Response _failHandler(Request request) {
+  fail('should never get here');
+  return null;
+}
 
 final Response _middlewareResponse =
     new Response.ok('middleware content', headers: {'from': 'middleware'});