Index: resources/data/validator/deprecated.mapcss
===================================================================
--- resources/data/validator/deprecated.mapcss	(revision 18230)
+++ resources/data/validator/deprecated.mapcss	(working copy)
@@ -2326,6 +2326,14 @@
   group: tr("deprecated tagging");
 }
 
+/* #21954 */
+*[surface=decoturf] {
+  throwWarning: tr("{0} is deprecated", "{0.tag}");
+  suggestAlternative: "surface=acrylic";
+  fixAdd: "surface=acrylic";
+  group: tr("deprecated tagging");
+}
+
 /* #20637 */
 *[role] {
   throwWarning: tr("{0} as a tag on an object. Roles are specified in the relation members list instead.", "{0.tag}", "{0.key}");
Index: resources/data/validator/ignoretags.cfg
===================================================================
--- resources/data/validator/ignoretags.cfg	(revision 18356)
+++ resources/data/validator/ignoretags.cfg	(working copy)
@@ -722,6 +722,7 @@
 K:man_made=pumping_rig
 E:pump:type
 K:substance=heat
+K:surface=decoturf
 ;
 ; Tags not yet decided (to remove from this section when added or moved up when deprecated) 
 ; see josm tickets: 17770 15309 15774 16315 16658 16793 19982