Index: trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 14486)
+++ trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 14489)
@@ -469,5 +469,5 @@
                     try {
                         final String val = ai.val instanceof Expression
-                                ? Optional.of(((Expression) ai.val).evaluate(new Environment())).map(Object::toString).orElse(null)
+                                ? Optional.ofNullable(((Expression) ai.val).evaluate(new Environment())).map(Object::toString).orElse(null)
                                 : ai.val instanceof String
                                 ? (String) ai.val
Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj	(revision 14486)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj	(revision 14489)
@@ -166,5 +166,4 @@
 {
     < IDENT: ["a"-"z","A"-"Z","_"] ( ["a"-"z","A"-"Z","_","-","0"-"9"] )* >
-|   < EXTIDENT: <MINUS> <IDENT> >
 |   < UINT: ( ["0"-"9"] )+ >
 |   < STRING: "\"" ( [" ","!","#"-"[","]"-"~","\u0080"-"\uFFFF"] | "\\\"" | "\\\\" )*  "\"" >
@@ -284,5 +283,5 @@
 {
     (
-        (t=<PP_AND> | t=<PP_OR> | t=<PP_NOT> | t=<UINT> | t=<STRING> | t=<REGEX> | t=<LPAR> | t=<RPAR> | t=<COMMA> | t=<COLON> | t=<IDENT> | t=<EXTIDENT> | t=<PP_SOMETHING_ELSE>) { if (write) sb.append(t.image); }
+        (t=<PP_AND> | t=<PP_OR> | t=<PP_NOT> | t=<UINT> | t=<STRING> | t=<REGEX> | t=<LPAR> | t=<RPAR> | t=<COMMA> | t=<COLON> | t=<IDENT> | t=<PP_SOMETHING_ELSE>) { if (write) sb.append(t.image); }
         |
             pp_w1()
@@ -907,5 +906,5 @@
         )
     |
-        <EXTIDENT> w() <COLON> w() expression() <SEMICOLON> w()
+        <MINUS> <IDENT> w() <COLON> w() expression() <SEMICOLON> w()
     |
         key=<IDENT> w() <COLON> w()