diff --git a/composer.json b/composer.json
index 7866820..5fa39d0 100644
--- a/composer.json
+++ b/composer.json
@@ -5,7 +5,7 @@
   "require": {
     "php": ">=5.5",
     "guzzlehttp/guzzle": "^6.3",
-    "monolog/monolog": "^1.0"
+    "monolog/monolog": "^2.0"
   },
   "require-dev": {
     "phpunit/phpunit": "^6.0"
@@ -20,4 +20,4 @@
   },
   "minimum-stability": "dev",
   "prefer-stable": true
-}
\ No newline at end of file
+}
diff --git a/src/ConvertKit_API.php b/src/ConvertKit_API.php
index c49a29e..4ddee17 100644
--- a/src/ConvertKit_API.php
+++ b/src/ConvertKit_API.php
@@ -417,6 +417,45 @@ public function get_subscriber( $subscriber_id ) {
 
     }
 
+    /**
+     * Update subscriber
+     *
+     * @param int   $subscriber_id Subscriber ID.
+     * @param array $data          Subscriber data.
+     * @return false|int
+     */
+    public function update_subscriber( $subscriber_id, $data ) {
+
+        if( !is_int($subscriber_id) || $subscriber_id < 1 ) {
+            throw new \InvalidArgumentException;
+        }
+
+        $request = $this->api_version . sprintf( '/subscribers/%s', $subscriber_id );
+
+        $options = array(
+            'api_secret' => $this->api_secret,
+        );
+
+        if ( array_key_exists( 'first_name', $data ) ) {
+          $options['first_name'] = $data['first_name'];
+          unset( $data['first_name'] );
+        }
+
+        if ( array_key_exists( 'email_address', $data ) ) {
+          $options['email_address'] = $data['email_address'];
+          unset( $data['email_address'] );
+        }
+
+        if ( $data ) {
+          $options['fields'] = $data;
+        }
+
+        $this->create_log(sprintf("PUT update subscriber: %s, %s, %s", $request, json_encode($options), $subscriber_id));
+
+        return $this->make_request( $request, 'PUT', $options );
+
+    }
+
     /**
      * Get a list of the tags for a subscriber.
      *