Let protoc_plugin depend on protobuf from null-safety and fix changelog. (#456)

diff --git a/protobuf/CHANGELOG.md b/protobuf/CHANGELOG.md
index 5cc1eb9..3254ed3 100644
--- a/protobuf/CHANGELOG.md
+++ b/protobuf/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 2.0.0-nullsafety.1
 
+* Protobuf messages can now be sent between isolates.
 * Remove `PbMap.add` method which was deprecated in 0.13.3
 
 ## 2.0.0-nullsafety.0
diff --git a/protoc_plugin/pubspec.yaml b/protoc_plugin/pubspec.yaml
index dcee5e2..37f8e6d 100644
--- a/protoc_plugin/pubspec.yaml
+++ b/protoc_plugin/pubspec.yaml
@@ -9,7 +9,7 @@
 dependencies:
   fixnum: '>=0.10.9 <2.0.0'
   path: ^1.0.0
-  protobuf: '>=1.1.0 <2.0.0'
+  protobuf: '^2.0.0-nullsafety.1'
   dart_style: ^1.0.6
 
 dev_dependencies: