Index: src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java
===================================================================
--- src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java	(revision 15944)
+++ src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java	(working copy)
@@ -70,7 +70,9 @@
 import org.openstreetmap.josm.command.Command;
 import org.openstreetmap.josm.command.SequenceCommand;
 import org.openstreetmap.josm.data.UndoRedoHandler;
+import org.openstreetmap.josm.data.coor.LatLon;
 import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.data.osm.INode;
 import org.openstreetmap.josm.data.osm.OsmDataManager;
 import org.openstreetmap.josm.data.osm.OsmPrimitive;
 import org.openstreetmap.josm.data.osm.OsmPrimitiveType;
@@ -692,6 +694,8 @@
             final Iterator<OsmPrimitive> osmPrimitiveIterator = sel.iterator();
             final OsmPrimitive virtual = (osmPrimitiveIterator.hasNext() ? osmPrimitiveIterator.next().getType() : OsmPrimitiveType.NODE)
                     .newInstance(0, false);
+            if (virtual instanceof INode)
+                ((INode) virtual).setCoor(LatLon.ZERO);
             virtual.put(key, value);
             final ImageIcon padded = ImageProvider.getPadded(virtual, ImageProvider.ImageSizes.LARGEICON.getImageDimension(),
                     EnumSet.of(ImageProvider.GetPaddedOptions.NO_DEFAULT, ImageProvider.GetPaddedOptions.NO_DEPRECATED));
Index: test/unit/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelperTest.java
===================================================================
--- test/unit/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelperTest.java	(revision 15944)
+++ test/unit/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelperTest.java	(working copy)
@@ -36,6 +36,7 @@
 import org.openstreetmap.josm.gui.mappaint.mapcss.MapCSSStyleSource;
 import org.openstreetmap.josm.testutils.JOSMTestRules;
 import org.openstreetmap.josm.testutils.mockers.WindowMocker;
+import org.openstreetmap.josm.tools.RightAndLefthandTraffic;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
@@ -49,7 +50,7 @@
      */
     @Rule
     @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
-    public JOSMTestRules test = new JOSMTestRules();
+    public JOSMTestRules test = new JOSMTestRules().territories().projection();
 
     private static TagEditHelper newTagEditHelper() {
         DefaultTableModel propertyData = new DefaultTableModel();
@@ -123,4 +124,43 @@
         Object val = findIcon.invoke(addTagsDialog, "highway", "");
         assertNotNull(val);
     }
+
+    /**
+     * Non-regression test for <a
+     * href="https://josm.openstreetmap.de/ticket/18798>#18798</a>
+     *
+     * @throws InvocationTargetException Check logs -- if caused by NPE, a
+     *                                   regression probably occurred.
+     * @throws IllegalArgumentException  Check source code
+     * @throws IllegalAccessException    Check source code
+     * @throws NoSuchFieldException      Check source code
+     * @throws SecurityException         Probably shouldn't happen for tests
+     * @throws NoSuchMethodException     Check source code
+     */
+    @Test
+    public void testTicket18798() throws NoSuchMethodException, SecurityException, IllegalAccessException,
+            IllegalArgumentException, InvocationTargetException, NoSuchFieldException {
+        TestUtils.assumeWorkingJMockit();
+        if (GraphicsEnvironment.isHeadless()) {
+            new WindowMocker();
+        }
+        RightAndLefthandTraffic.initialize();
+        MapCSSStyleSource css = new MapCSSStyleSource(
+                "node:righthandtraffic[junction=roundabout] { text: tr(\"Roundabout node\"); }");
+        css.loadStyleSource();
+        MapPaintStyles.addStyle(css);
+        Node node = new Node(LatLon.NORTH_POLE);
+        DataSet ds = new DataSet(node);
+        OsmDataManager.getInstance().setActiveDataSet(ds);
+        MainApplication.getLayerManager().addLayer(new OsmDataLayer(ds, "Test Layer", null));
+        TagEditHelper helper = newTagEditHelper();
+        Field sel = TagEditHelper.class.getDeclaredField("sel");
+        sel.set(helper, Collections.singletonList(node));
+        AddTagsDialog addTagsDialog = helper.getAddTagsDialog();
+        Method findIcon = TagEditHelper.AbstractTagsDialog.class.getDeclaredMethod("findIcon", String.class,
+                String.class);
+        findIcon.setAccessible(true);
+        Object val = findIcon.invoke(addTagsDialog, "junction", "roundabout");
+        assertNotNull(val);
+    }
 }