Index: trunk/data/validator/combinations.mapcss
===================================================================
--- trunk/data/validator/combinations.mapcss	(revision 15105)
+++ trunk/data/validator/combinations.mapcss	(revision 15110)
@@ -223,5 +223,7 @@
 }
 
-/* {0.tag} together with {1.key}, see #17707, #16464, #10837, #14034, #9389, #11977, #13156, #16888 */
+/* {0.tag} together with {1.key}, see #17664, #17707, #16464, #10837, #14034, #9389, #11977, #13156, #16888 */
+*[power=plant][/^generator:/],
+*[power=generator][/^plant:/],
 *[power=plant][voltage],
 *[power=plant][frequency],
@@ -237,4 +239,6 @@
   throwWarning: tr("{0} together with {1}", "{0.tag}", "{1.key}");
   group: tr("suspicious tag combination");
+  assertMatch: "way power=plant generator:source=wind";
+  assertMatch: "way power=generator plant:source=combustion";
 }