diff --git a/mef/schema/mission_phase.rnc b/mef/schema/mission_phase.rnc
index e52cad9..7f7033c 100644
--- a/mef/schema/mission_phase.rnc
+++ b/mef/schema/mission_phase.rnc
@@ -9,5 +9,5 @@ phase-definition =
     attribute time-fraction { xsd:double },
     label?,
     attributes?,
-    instruction*
+    (set-house-event | set-parameter)*
   }