Index: /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 14539)
+++ /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 14540)
@@ -993,5 +993,5 @@
                 .map(e -> ((LiteralExpression) e).getLiteral())
                 .filter(l -> l instanceof String)
-                .map(l -> (String) l)
+                .map(l -> ((String) l).split(",")[0])
                 .findFirst();
     }
Index: /trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java
===================================================================
--- /trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java	(revision 14539)
+++ /trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java	(revision 14540)
@@ -207,4 +207,20 @@
 
     /**
+     * Non-regression test for <a href="https://josm.openstreetmap.de/ticket/17058">Bug #17058</a>.
+     * @throws ParseException if a parsing error occurs
+     */
+    @Test
+    public void testTicket17058() throws ParseException {
+        final MapCSSTagChecker test = buildTagChecker(
+                "*[name =~ /(?i).*Straße.*/][inside(\"LI,CH\")] {\n" +
+                "  throwError: tr(\"street name contains ß\");\n" +
+                "  assertMatch: \"way name=Hauptstraße\";\n" +
+                "  assertNoMatch: \"way name=Hauptstrasse\";\n" +
+                "}");
+        Set<String> errors = test.checkAsserts(test.checks.get("test"));
+        assertTrue(errors.toString(), errors.isEmpty());
+    }
+
+    /**
      * Non-regression test for <a href="https://josm.openstreetmap.de/ticket/13762">Bug #13762</a>.
      * @throws ParseException if a parsing error occurs