diff --git a/controllers/API.php b/controllers/API.php
index be65c20..ae9fc63 100644
--- a/controllers/API.php
+++ b/controllers/API.php
@@ -105,7 +105,7 @@ class API {
       $domain = parse_url($url, PHP_URL_HOST);
       if($url == $target || $domain == $target_domain ||
          # subdomain check
-         ($target_domain and substr_compare($domain, '.' . $target_domain, -(strlen($target_domain) + 1)) == 0)) {
+         ($target_domain and $domain and substr_compare($domain, '.' . $target_domain, -(strlen($target_domain) + 1)) == 0)) {
         $found[$url] = null;
       }
     }
diff --git a/tests/APITest.php b/tests/APITest.php
index 200155b..526ce28 100644
--- a/tests/APITest.php
+++ b/tests/APITest.php
@@ -52,9 +52,8 @@ class APITest extends PHPUnit_Framework_TestCase {
 
     # Verify it queued the mention in the database
     $d = ORM::for_table('webmentions')->where(['source' => $source, 'target' => $target])->find_one();
-    $this->assertNotNull($d);
+    $this->assertNotFalse($d);
     $this->assertEquals($match[1], $d->token);
-
     # Check the status endpoint to make sure it says it's still queued
     $response = $this->status($d->token);
     $this->assertEquals(200, $response->getStatusCode());
@@ -62,6 +61,12 @@ class APITest extends PHPUnit_Framework_TestCase {
     $this->assertEquals('queued', $data->status);
   }
 
+  private function _assertNotQueued($source, $target) {
+    # Verify it did not queue a mention in the database
+    $d = ORM::for_table('webmentions')->where(['source' => $source, 'target' => $target])->find_one();
+    $this->assertFalse($d);
+  }
+
   public function testAuthentication() {
     $response = $this->webmention([]);
     $this->assertEquals(401, $response->getStatusCode());
@@ -192,6 +197,23 @@ class APITest extends PHPUnit_Framework_TestCase {
     $this->_assertQueued('http://source.example.com/basictest', 'http://target2.example.com', $data->location[1]);
   }
 
+  public function testTargetDomainQueuesOnlyWebmentionsFromTargetDomain() {
+    $this->_createExampleAccount();
+
+    $response = $this->webmention(['token'=>'a','source'=>'http://source.example.com/multipletest','target_domain'=>'example.com']);
+    $body = $response->getContent();
+    $this->assertEquals(201, $response->getStatusCode(), $body);
+    $data = json_decode($body);
+    $this->assertEquals(false, property_exists($data, 'error'), $body);
+    $this->assertEquals('queued', $data->status, $body);
+    $this->assertEquals(2, count($data->location), $body);
+    $this->_assertQueued('http://source.example.com/multipletest', 'http://target.example.com', $data->location[0]);
+    $this->_assertQueued('http://source.example.com/multipletest', 'http://target2.example.com', $data->location[1]);
+    $this->_assertNotQueued('http://source.example.com/multipletest', 'http://target.example.org');
+    $this->_assertNotQueued('http://source.example.com/multipletest', '/relativelink');
+    $this->_assertNotQueued('http://source.example.com/multipletest', 'http://source.example.com/relativelink');
+  }
+
   public function testStatusNotFound() {
     $this->_createExampleAccount();