diff --git a/composer.json b/composer.json
index 755ea4b..9758994 100644
--- a/composer.json
+++ b/composer.json
@@ -1,21 +1,18 @@
 {
-  "name": "grpc/grpc",
+  "name": "grpc/grpc",  
   "type": "library",
   "description": "gRPC library for PHP",
   "keywords": ["rpc"],
   "homepage": "https://grpc.io",
   "license": "Apache-2.0",
-  "version": "1.57.0",
+  "version": "1.73.0",
   "require": {
-    "php": ">=7.0.0"
+    "php": ">=7.0.0",
+    "google/protobuf": "^v3.3.0"
   },
   "require-dev": {
     "google/auth": "^v1.3.0"
   },
-  "suggest": {
-    "ext-protobuf": "For better performance, install the protobuf C extension.",
-    "google/protobuf": "To get started using grpc quickly, install the native protobuf library."
-  },
   "autoload": {
     "psr-4": {
       "Grpc\\": "src/lib/"
diff --git a/etc/README.md b/etc/README.md
new file mode 100644
index 0000000..87af44f
--- /dev/null
+++ b/etc/README.md
@@ -0,0 +1,4 @@
+The roots.pem file is periodically generated from:
+https://hg.mozilla.org/mozilla-central/raw-file/tip/security/nss/lib/ckfw/builtins/certdata.txt
+using
+https://github.com/agl/extract-nss-root-certs
diff --git a/src/lib/BaseStub.php b/src/lib/BaseStub.php
index d9da4ca..97d0b24 100644
--- a/src/lib/BaseStub.php
+++ b/src/lib/BaseStub.php
@@ -228,7 +228,7 @@ private function _get_jwt_aud_uri($method)
         }
 
         // Remove the port if it is 443
-        // See https://github.com/grpc/grpc/blob/07c9f7a36b2a0d34fcffebc85649cf3b8c339b5d/src/core/lib/security/transport/client_auth_filter.cc#L205
+        // See https://github.com/grpc/grpc/blob/07c9f7a36b2a0d34fcffebc85649cf3b8c339b5d/src/core/filter/auth/client_auth_filter.cc#L205
         if ((strlen($hostname) > 4) && (substr($hostname, -4) === ":443")) {
             $hostname = substr($hostname, 0, -4);
         }