Index: trunk/data/validator/combinations.mapcss
===================================================================
--- trunk/data/validator/combinations.mapcss	(revision 8120)
+++ trunk/data/validator/combinations.mapcss	(revision 8121)
@@ -46,4 +46,5 @@
 *[border_type                  ][!boundary],
 *[bridge:structure             ][!bridge],
+*[piste:difficulty             ][!piste:type],
 *[source:date                  ][!source],
 *[source:name                  ][!name],
@@ -239,5 +240,5 @@
 
 /* see #9593, #11183 */
-*[sport][!building][tourism != hotel][highway != raceway][leisure !~ /^(sports_centre|stadium|track|pitch|golf_course|water_park|swimming_pool|recreation_ground)$/][natural !~ /^(beach|bare_rock|peak)$/][amenity !~ /^(pub|restaurant|swimming_pool)$/][landuse !~ /^(recreation_ground|piste|farm|farmland)$/][barrier !~ /^(wall|retaining_wall)$/] {
+*[sport][!building][tourism != hotel][highway != raceway][leisure !~ /^(sports_centre|stadium|track|pitch|golf_course|water_park|swimming_pool|recreation_ground)$/][natural !~ /^(beach|bare_rock|peak)$/][amenity !~ /^(pub|restaurant|swimming_pool)$/][landuse !~ /^(recreation_ground|piste|farm|farmland)$/][barrier !~ /^(wall|retaining_wall)$/][!"piste:type"] {
     throwWarning: tr("sport without physical feature");
     assertMatch: "node sport=tennis";
Index: trunk/data/validator/deprecated.mapcss
===================================================================
--- trunk/data/validator/deprecated.mapcss	(revision 8120)
+++ trunk/data/validator/deprecated.mapcss	(revision 8121)
@@ -392,2 +392,8 @@
   throwWarning: tr("Unspecific tag {0}", "{0.tag}");
 }
+
+/* unclear definition, see #11183 */
+*[sport=skiing][!piste:type] {
+  throwWarning: tr("Definition of {0} is unclear", "{0.tag}");
+  suggestAlternative: {1.key};
+}