diff --git a/.circleci/config.yml b/.circleci/config.yml
index 964063f8f1e..373948713d4 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -64,7 +64,7 @@ jobs:
             EOF
       - run:
           name: Check that Bazel BUILD files are up-to-date
-          command: 'bazel run //:gazelle ||
+          command: 'bazel run //:gazelle -- --mode=diff ||
             (echo "ERROR: Bazel files out-of-date, please run \`bazel run :gazelle\`" >&2; exit 1)'
       - run:
           name: Run tests with Bazel
diff --git a/runtime/BUILD.bazel b/runtime/BUILD.bazel
index c99f83e5851..20862228ef8 100644
--- a/runtime/BUILD.bazel
+++ b/runtime/BUILD.bazel
@@ -11,6 +11,7 @@ go_library(
         "errors.go",
         "fieldmask.go",
         "handler.go",
+        "marshal_httpbodyproto.go",
         "marshal_json.go",
         "marshal_jsonpb.go",
         "marshal_proto.go",
@@ -29,6 +30,7 @@ go_library(
         "@com_github_golang_protobuf//jsonpb:go_default_library_gen",
         "@com_github_golang_protobuf//proto:go_default_library",
         "@com_github_golang_protobuf//protoc-gen-go/generator:go_default_library_gen",
+        "@go_googleapis//google/api:httpbody_go_proto",
         "@io_bazel_rules_go//proto/wkt:any_go_proto",
         "@io_bazel_rules_go//proto/wkt:duration_go_proto",
         "@io_bazel_rules_go//proto/wkt:field_mask_go_proto",
@@ -49,6 +51,7 @@ go_test(
         "errors_test.go",
         "fieldmask_test.go",
         "handler_test.go",
+        "marshal_httpbodyproto_test.go",
         "marshal_json_test.go",
         "marshal_jsonpb_test.go",
         "marshal_proto_test.go",
@@ -65,6 +68,7 @@ go_test(
         "@com_github_golang_protobuf//jsonpb:go_default_library_gen",
         "@com_github_golang_protobuf//proto:go_default_library",
         "@com_github_golang_protobuf//ptypes:go_default_library_gen",
+        "@go_googleapis//google/api:httpbody_go_proto",
         "@go_googleapis//google/rpc:errdetails_go_proto",
         "@io_bazel_rules_go//proto/wkt:duration_go_proto",
         "@io_bazel_rules_go//proto/wkt:empty_go_proto",