diff --git a/api/src/Link.php b/api/src/Link.php
index 68298cfb91..386d01ca99 100644
--- a/api/src/Link.php
+++ b/api/src/Link.php
@@ -683,15 +683,15 @@ class Link extends Link\Storage
 		{
 			echo "<p>Link::unlink('$link_id','$app',".array2string($id).",'$owner','$app2','$id2', $hold_for_purge)</p>\n";
 		}
-		if ($link_id < 0)	// vfs-link?
+		if ((int)$link_id < 0)	// vfs-link?
 		{
 			return self::delete_attached(-$link_id);
 		}
-		elseif ($app == self::VFS_APPNAME)
+		elseif ($app === self::VFS_APPNAME)
 		{
 			return self::delete_attached($app2,$id2,$id);
 		}
-		elseif ($app2 == self::VFS_APPNAME)
+		elseif ($app2 === self::VFS_APPNAME)
 		{
 			return self::delete_attached($app,$id,$id2);
 		}