diff --git a/lib/DbMapping.php b/lib/DbMapping.php
index b6973d7..c0a1c06 100644
--- a/lib/DbMapping.php
+++ b/lib/DbMapping.php
@@ -108,7 +108,9 @@ abstract class DbMapping
      * @param int $id
      * @return DbMapping
      */
-    abstract public static function find($id);
+    public static function find($id) {
+        throw new RuntimeException("This method must be implemented in child classes.");
+    }
 
     /**
      * Return all the public attributes in an array;