diff --git a/data/schema/core/actionwml.cfg b/data/schema/core/actionwml.cfg
index fd107450c497..17eebe711ad8 100644
--- a/data/schema/core/actionwml.cfg
+++ b/data/schema/core/actionwml.cfg
@@ -375,7 +375,6 @@
 		{INSERT_TAG}
 		{DEFAULT_KEY take_only_once s_bool yes}
 		{DEFAULT_KEY delayed_variable_substitution s_bool no}
-		{SIMPLE_KEY duration object_duration}
 		{SIMPLE_KEY silent s_bool}
 		{SIMPLE_KEY image string}
 		{SIMPLE_KEY name t_string}
diff --git a/data/schema/units/modifications.cfg b/data/schema/units/modifications.cfg
index d396b6775135..86c14635fdd6 100644
--- a/data/schema/units/modifications.cfg
+++ b/data/schema/units/modifications.cfg
@@ -253,4 +253,5 @@
 	name="object"
 	max=infinite
 	super="units/$modifications/base"
+	{SIMPLE_KEY duration object_duration}
 [/tag]