diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..987e2a2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+composer.lock
+vendor
diff --git a/composer.json b/composer.json
index 755ea4b..28e457d 100644
--- a/composer.json
+++ b/composer.json
@@ -5,9 +5,10 @@
   "keywords": ["rpc"],
   "homepage": "https://grpc.io",
   "license": "Apache-2.0",
-  "version": "1.57.0",
+  "version": "1.74.0",
   "require": {
-    "php": ">=7.0.0"
+    "php": ">=7.1.0",
+    "google/protobuf": "^v3.3.0"
   },
   "require-dev": {
     "google/auth": "^v1.3.0"
diff --git a/src/lib/ServerCallWriter.php b/src/lib/ServerCallWriter.php
index aceb20c..40fbe99 100644
--- a/src/lib/ServerCallWriter.php
+++ b/src/lib/ServerCallWriter.php
@@ -81,7 +81,7 @@ public function finish(
 
     private function addSendInitialMetadataOpIfNotSent(
         array &$batch,
-        array $initialMetadata = null
+        ?array $initialMetadata = null
     ) {
         if (!$this->initialMetadataSent_) {
             $batch[OP_SEND_INITIAL_METADATA] = $initialMetadata ?? [];
diff --git a/src/lib/Status.php b/src/lib/Status.php
index add208f..d47480f 100644
--- a/src/lib/Status.php
+++ b/src/lib/Status.php
@@ -32,7 +32,7 @@
  */
 class Status
 {
-    public static function status(int $code, string $details, array $metadata = null): array
+    public static function status(int $code, string $details, ?array $metadata = null): array
     {
         $status = [
             'code' => $code,
@@ -44,7 +44,7 @@ public static function status(int $code, string $details, array $metadata = null
         return $status;
     }
 
-    public static function ok(array $metadata = null): array
+    public static function ok(?array $metadata = null): array
     {
         return Status::status(STATUS_OK, 'OK', $metadata);
     }
diff --git a/src/lib/UnaryCall.php b/src/lib/UnaryCall.php
index e849649..76d96cc 100644
--- a/src/lib/UnaryCall.php
+++ b/src/lib/UnaryCall.php
@@ -22,6 +22,8 @@
 /**
  * Represents an active call that sends a single message and then gets a
  * single response.
+ *
+ * @template T of \Google\Protobuf\Internal\Message
  */
 class UnaryCall extends AbstractCall
 {
@@ -50,7 +52,7 @@ public function start($data, array $metadata = [], array $options = [])
     /**
      * Wait for the server to respond with data and a status.
      *
-     * @return array [response data, status]
+     * @return array{0: T|null, 1: \stdClass} [response data, status]
      */
     public function wait()
     {