diff --git a/unstable/wlr-data-control-unstable-v1.xml b/unstable/wlr-data-control-unstable-v1.xml
index bc6f2ab..0a4dc24 100644
--- a/unstable/wlr-data-control-unstable-v1.xml
+++ b/unstable/wlr-data-control-unstable-v1.xml
@@ -83,6 +83,9 @@
         This request asks the compositor to set the selection to the data from
         the source on behalf of the client.
 
+        The given source may not be used in any further set_selection or
+        set_primary_selection requests.
+
         To unset the selection, set the source to NULL.
       </description>
       <arg name="source" type="object" interface="zwlr_data_control_source_v1"
@@ -162,6 +165,9 @@
         This request asks the compositor to set the primary selection to the
         data from the source on behalf of the client.
 
+        The given source may not be used in any further set_selection or
+        set_primary_selection requests.
+
         To unset the primary selection, set the source to NULL.
 
         The compositor will ignore this request if it does not support primary