Index: /trunk/.github/workflows/ant.yml
===================================================================
--- /trunk/.github/workflows/ant.yml	(revision 17154)
+++ /trunk/.github/workflows/ant.yml	(revision 17155)
@@ -17,4 +17,6 @@
   build:
     runs-on: ${{ matrix.os }}
+    env:
+      LANG: en_US.UTF-8
     strategy:
       fail-fast: false
Index: /trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java
===================================================================
--- /trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java	(revision 17154)
+++ /trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java	(revision 17155)
@@ -4,4 +4,5 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import java.text.DecimalFormat;
@@ -29,8 +30,7 @@
     @Test
     public void testGroupingSeparator() {
-        if (Utils.getJavaVersion() < 9) {
-            // not supported
-            return;
-        }
+        System.out.println(Locale.getDefault());
+        assumeTrue(Utils.getJavaVersion() >= 9);
+
         assertTrue(I18n.getAvailableTranslations().count() > 10);
         I18n.getAvailableTranslations().forEach(this::checkGroupingSymbol);