diff --git a/src/Firebase/Messaging/WebPushConfig.php b/src/Firebase/Messaging/WebPushConfig.php
index 55204433..1e90fc3d 100644
--- a/src/Firebase/Messaging/WebPushConfig.php
+++ b/src/Firebase/Messaging/WebPushConfig.php
@@ -10,7 +10,7 @@
 /**
  * @see https://tools.ietf.org/html/rfc8030#section-5.3 Web Push Message Urgency
  * @phpstan-type WebPushHeadersShape array{
- *     TTL?: positive-int|numeric-string,
+ *     TTL?: positive-int|numeric-string|null,
  *     Urgency?: self::URGENCY_*
  * }
  *
@@ -91,6 +91,10 @@ public static function fromArray(array $config): self
     {
         if (array_key_exists('headers', $config) && is_array($config['headers'])) {
             $config['headers'] = self::ensureValidHeaders($config['headers']);
+
+            if ($config['headers'] === []) {
+                unset($config['headers']);
+            }
         }
 
         return new self($config);
@@ -103,16 +107,18 @@ public static function fromArray(array $config): self
      */
     private static function ensureValidHeaders(array $headers): array
     {
-        if (array_key_exists('TTL', $headers) && is_int($headers['TTL'])) {
-            $headers['TTL'] = (string) $headers['TTL'];
-        }
+        if (array_key_exists('TTL', $headers)) {
+            if (is_int($headers['TTL'])) {
+                $headers['TTL'] = (string) $headers['TTL'];
+            }
 
-        if (
-            array_key_exists('TTL', $headers)
-            && is_string($headers['TTL'])
-            && preg_match('/^[\-0]/', $headers['TTL']) === 1
-        ) {
-            throw new InvalidArgument('The TTL in the WebPushConfig must must be a positive int');
+            if (is_string($headers['TTL']) && (preg_match('/^[1-9]\d*$/', $headers['TTL']) !== 1)) {
+                throw new InvalidArgument('The TTL in the WebPushConfig must must be a positive int');
+            }
+
+            if ($headers['TTL'] === null) {
+                unset($headers['TTL']);
+            }
         }
 
         if (array_key_exists('Urgency', $headers)) {
diff --git a/tests/Unit/Messaging/WebPushConfigTest.php b/tests/Unit/Messaging/WebPushConfigTest.php
index 160f51f3..2672f4cd 100644
--- a/tests/Unit/Messaging/WebPushConfigTest.php
+++ b/tests/Unit/Messaging/WebPushConfigTest.php
@@ -42,6 +42,18 @@ public function testItCanHaveAPriority(): void
         $this->assertSame('high', $config->jsonSerialize()['headers']['Urgency']);
     }
 
+    /**
+     * @dataProvider validHeaders
+     *
+     * @param WebPushHeadersShape $headers
+     */
+    public function testItAcceptsValidHeaders(array $headers): void
+    {
+        WebPushConfig::fromArray(['headers' => $headers]);
+
+        $this->addToAssertionCount(1);
+    }
+
     /**
      * @dataProvider invalidHeaders
      *
@@ -82,6 +94,7 @@ public function validHeaders(): array
         return [
             'positive int ttl' => [['TTL' => 1]],
             'positive string ttl' => [['TTL' => '1']],
+            'null (#719)' => [['TTL' => null]],
         ];
     }
 
@@ -93,8 +106,8 @@ public function invalidHeaders(): array
         return [
             'negative int ttl' => [['TTL' => -1]],
             'negative string ttl' => [['TTL' => '-1']],
-            'zero int ttl' => [['TTL' => -1]],
-            'zero string ttl' => [['TTL' => '-1']],
+            'zero int ttl' => [['TTL' => 0]],
+            'zero string ttl' => [['TTL' => '0']],
             'unsupported urgency' => [['Urgency' => 'unsupported']],
         ];
     }