diff --git a/sismic/io/yaml.py b/sismic/io/yaml.py
index d9d054d..8d92341 100644
--- a/sismic/io/yaml.py
+++ b/sismic/io/yaml.py
@@ -34,6 +34,7 @@ class SCHEMA:
         schema.Optional('initial'): schema.Use(str),
         schema.Optional('parallel states'): [state],
         schema.Optional('states'): [state],
+        schema.Optional('memory'): schema.Use(str),
     })
 
     statechart = {