diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 48be78e6fc..00bf9db3d9 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -3269,7 +3269,11 @@ function attachment_url_to_postid( $url ) {
 	global $wpdb;
 
 	$dir = wp_upload_dir();
-	$path = ltrim( $url, $dir['baseurl'] . '/' );
+	$path = $url;
+
+	if ( 0 === strpos( $path, $dir['baseurl'] . '/' ) ) {
+		$path = substr( $path, strlen( $dir['baseurl'] . '/' ) );
+	}
 
 	$sql = $wpdb->prepare(
 		"SELECT post_id FROM $wpdb->postmeta WHERE meta_key = '_wp_attached_file' AND meta_value = %s",
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 506367f8b1..c22bf623fc 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -443,4 +443,28 @@ VIDEO;
 		$this->assertTrue( has_image_size( 'test-size' ) );
 	}
 
+	/**
+	 * @ticket 30346
+	 */
+	function test_attachment_url_to_postid() {
+		$image_path = '2014/11/' . $this->img_name;
+		$attachment_id = $this->factory->attachment->create_object( $image_path, 0, array(
+			'post_mime_type' => 'image/jpeg',
+			'post_type'      => 'attachment',
+		) );
+
+		$image_url  = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . $image_path;
+		$this->assertEquals( $attachment_id, attachment_url_to_postid( $image_url ) );
+
+		add_filter( 'upload_dir', array( $this, '_upload_dir' ) );
+		$image_url = 'http://192.168.1.20.com/wp-content/uploads/' . $image_path;
+		$this->assertEquals( $attachment_id, attachment_url_to_postid( $image_url ) );
+		remove_filter( 'upload_dir', array( $this, '_upload_dir' ) );
+	}
+
+	function _upload_dir( $dir ) {
+		$dir['baseurl'] = 'http://192.168.1.20.com/wp-content/uploads';
+		return $dir;
+	}
+
 }